Among the standard light sources, three sources (namely, Spot, Direct and Omni) allow us to choose the type of shadow being calculated. If we use the standard Default Scanline Renderer (DSR) visualizer, then we will be interested in: Advanced ray-traced shadows, Area shadows, Ray-traced shadows, Shadow maps.
When choosing the type of shadow among the scrolls of the IP parameters, a scroll of shadow parameters appears, the name of which begins with the type name.
Shadow map
The simplest and most undemanding type of shadow to calculated resources.
- The size of the map based on which the shadow is calculated. The larger the map, the better the calculated shadow. Better to use numbers of order 2 n
- Blur the edge of the shadow. Increasing the parameter allows you to get rid of the serrated edge of the edge with a low resolution map
- Parameter responsible for controlling the Bias value. Disabled by default (best result in most cases). In the case of animation, enabling the option may help.
- If it is turned off, then the light passes through the surface, if it stumbles upon the polygons, the normals facing away from it. Enabling the option allows you to get the correct shadows.
In Fig. 1, the top row of images visually shows a change in the quality of the shadow as the Size parameter increases. Even a significant increase in the size of the map does not solve the problem of teeth at the edges of the shadow, although the shadow pattern is certainly becoming more elaborate.
In the second row, in all three cases, the card size remains the same, but the Sample Range parameter changes. Gradually increasing it, we got rid of jagging, blurring the edge of the shadow.
Fig. 1 Changing the quality of a Shadow Map type shadow with various parameters
Ray-traced shadows
Shadows of this type are calculated based on the tracing algorithm. They have clear edges and are almost impossible to customize.
The Ray-Traced Shadow is more accurate with respect to the Shadow Map. In addition, it is able to take into account the transparency of the object, but meanwhile it is “dry” and clear, which does not look very natural in most cases. Ray-Traced Shadow is more demanding on computer resources than Shadow Map.
- Object distance from cast shadow
- The depth of the tracing is the parameter responsible for working out the shadow. Increasing this value can significantly increase imaging time.
Ray-Traced Shadows with Omni type ICs will take longer to render than a bunch of Ray-Traced Shadows + Spot (or Directional)
Fig. 2 Ray-Traced Shadows from opaque and transparent objects.
Advanced ray-traced shadows
Shadows of this type are very similar to Ray-Traced Shadows, but as the name implies, they have more advanced settings that allow you to get more natural and correct calculations.
- Shadow Generation Method
Simple - a single beam exits the IP. The shadow does not support any smoothing and quality settings
1-Pass Antialias - The emission of a beam of rays is imitated. Moreover, the same number of rays is reflected from each illuminated surface (the number of rays is regulated by Shadow Quality).
2-Pass Antialias - Similarly, but two beams of rays are emitted. - If it is off, then the light passes through the surface, if it comes across the polygons facing the normals from it. Enabling the option allows you to get the correct shadows.
- The number of rays emitted by the illuminated surface
- The number of secondary rays emitted by the illuminated surface
- The radius (in pixels) of the blur of the shadow edge. Increasing the parameter improves the quality of the blur. If small details are lost at the edge blur, adjust this case by increasing Shadow Integrity.
- Object distance from cast shadow
- The parameter that controls the randomness of the rays. Initially, the rays are sent along a strict grid, which can cause unpleasant artifacts. Introducing chaos will make the image of the shadow more natural
Recommended values \u200b\u200bare 0.5-1.0. But more blurry shadows will require more Jitter Amount
Area shadows
This type of shadows allows you to take into account the dimensions of the light source, so you can get natural long shadows that "split" and blur when moving away from the object. 3dsMax gets such shadows by mixing a number of “samples” (samples) of shadows. The more “samples” and the better the mix, the better the calculated shadow.
- The shape of an imaginary light source that allows you to determine the nature of the shadow.
Simple - a single beam exits the IP. The shadow does not support any smoothing and quality settings.
Rectangle ligh t - simulates the emission of light from a rectangular region.
Disc light - IP behaves as if it had acquired the form of a disk.
Box light - imitation of cubic IP.
Sphere ligh t - imitation of a spherical IP. - If it is turned off, then the light passes through the surface, if it stumbles upon the polygons, the normals facing away from it. Enabling the option allows you to get the correct shadow.
- Controls the number of rays emitted (non-linear). The higher the number, the more rays, the higher the quality of the shadow.
- The parameter responsible for the quality of the shadow. For a rational calculation, always set the number higher than Shadow Integrity.
- The radius (in pixels) of the blur of the shadow edge. Increasing the parameter improves the quality of the blur. If small details are lost at the edge blur, correct this incident with an increase in Shadow Integrity.
- The distance of the object from the cast shadow.
- The parameter that controls the randomness of the rays. Initially, the rays are sent along a strict grid, which can cause unpleasant artifacts. Introducing chaos will make the image of the shadow more natural.
- Dimensions of an imaginary source. Length - length, Width - width, Height (active only for Box Light and Sphere Light) - height.
Take a look at Figure 3. On the first fragment. Several “samples” of shadow are superimposed on each other without any mixing. In the second fragment they are already mixed (Jitter Amount changed from 0.0 to 6.0). Mixed “samples” are perceived as a more natural shadow, but its quality leaves much to be desired. The third fragment shows a shadow with excellent quality (Shadow Integrity and Shadow Quality are changed from single values \u200b\u200bto 8 and 10, respectively).
Second row in Fig. 3. illustrates how the nature of the shadow changes if we increase the size of the imaginary source. In this case, we have an imaginary source of the type Rectangle Light (flat rectangular). As the area of \u200b\u200bthe source increases, the blur of the shadow increases.
Fig. 3 Changing the quality of a shadow of type Area Shadow for various parameters
Some parameter values \u200b\u200bare advisory in nature, but everything is limited only by your imagination. The best way to figure it out is to experiment. Do not be afraid to experiment with light. Catch the mood of the future picture and surrender to the settings.
In Fig. 4. chess horse with material based on the simple procedural texture of Wood. Three light sources painted in different colors. A simple setting, however, the figure looks good.
Fig. 4 Chess piece "Horse". Subject visualization
Summary
Lighting is one of the most important stages in working on a three-dimensional scene. At first glance, it may seem that the dry lesson information cannot be applied to creative work. However, with proper ingenuity and hard work, you can achieve incredible results. In the end, all digital images are just sets of zeros and ones, and 3dsMax is just your next tool, just like a pencil or brush.
V-Ray is one of the most popular plugins for creating photorealistic visualizations. Its distinguishing feature is ease of setup and the ability to obtain high-quality results. Using V-Ray, used in the 3ds Max environment, they create materials, lighting and cameras, the interaction of which in the scene leads to the rapid creation of a naturalistic image.
In this article, we will learn about lighting settings using V-Ray. Correct light is very important for the correct creation of visualization. It should reveal all the best qualities of objects in the scene, create natural shadows and provide protection from noise, overexposure and other artifacts. Consider V-Ray tools for adjusting lighting.
1. First of all, download and install V-Ray. We go to the developer's site and select the version of V-Ray intended for 3ds Max. Download it. To download the program, register on the site.
2. Install the program following the prompts of the installation wizard.
3. Run 3ds Max, press the F10 key. Before us is the render settings panel. On the “Common” tab, find the “Assign Renderer” scroll and select V-Ray. Click “Save as defaults”.
Lighting can be of different types depending on the characteristics of the scene. Of course, lighting for subject visualization will differ from the light settings for the exterior. Consider a few basic lighting schemes.
Light customization for exterior visualization
1. Open the scene in which the lighting will be adjusted.
2. Install the light source. We will imitate the sun. On the Create tab of the toolbar, select “Lights” and click “V-Ray Sun”.
3. Indicate the start and end point of the rays of the sun. The angle between the beam and the surface of the earth will determine the morning, afternoon or evening type of atmosphere.
4. Select the sun and go to the “Modify” tab. We are interested in the following options:
- Enabled - enables and disables the sun.
- Turbidity - the higher this value - the greater the dustiness of the atmosphere.
- Intensity multiplier - a parameter that regulates the brightness of sunlight.
- Size multiplier - the size of the sun. the larger the parameter, the more blurry the shadows will be.
- Shadow subdivs - the higher this number, the better the shadow.
5. This completes the setting of the sun. Adjust the sky to make it more realistic. Press the "8" key, the environmental panel will open. Select the DefaultVraySky map as the environment map, as shown in the screenshot.
6. Without closing the environment panel, press the M key, opening the material editor. Drag the DefaultVraySky map from the slot in the environment panel to the material editor while holding the left mouse button.
7. We edit the sky map in the material browser. With the map highlighted, check the “Specify sun node” checkbox. Click “None” in the “Sun light” box and click on the sun in a model view. We just tied the sun and sky. Now the position of the sun will determine the brightness of the sky, fully simulating the state of the atmosphere at any time of the day. The rest of the settings will be left by default.
8. In general terms, exterior lighting is customized. Run renderings and experiment with light to achieve the desired effects.
For example, to create an atmosphere of a cloudy day, turn off the sun in its parameters and leave only the sky or HDRI map shining.
Light customization for subject visualization
1. Open the scene with the finished composition for visualization.
2. On the "Create" tab of the toolbar, select "Lights" and click "V-Ray Light".
3. Click in the projection where you want to set the light source. In this example, we place the light in front of the object.
4. Set the parameters of the light source.
- Type - this parameter sets the shape of the source: flat, spherical, dome. Shape is important when the light source is visible in the scene. For our case, let Plane remain the default (flat).
- Intensity - allows you to set the color strength in lumens or relative values. We leave relative ones - they are easier to regulate. The higher the number in the Multiplier line, the brighter the light.
- Color - determines the color of the light.
- Invisible - the light source can be made invisible in the scene, but it will continue to shine.
- Sampling - the “Subdivides” parameter controls the quality of rendering light and shadows. The higher the number in the line, the higher the quality.
The remaining parameters are best left as default.
5. For object visualization, it is recommended to install several light sources of different sizes, light intensity and distance from the object. Place two more light sources on the side of the subject. You can rotate them relative to the scene and adjust their parameters.
This method is not a "magic pill" for perfect lighting, but it simulates a real photo studio, experimenting in which you will achieve a very high-quality result.
Lighting a scene requires no less effort than modeling it, because in most cases it is necessary to provide a realistic effect. This is not an easy task, because in the real world light sources do not work at all like in the virtual one. For example, light is not reflected from the surfaces of objects - as a result, if in reality a single bulb can illuminate an entire room, including its areas hidden from direct rays of light (diffuse scattering), then in 3D Studio MAX such areas will remain completely dark. This means that diffuse light scattering will have to be simulated by additional lighting. And vice versa, virtual light sources can be configured so that they will not increase, but decrease the illumination of the scene, which in reality is impossible in principle, etc.
Properly selected lighting is one of the most significant factors in ensuring the realism of the scene during its visualization. It creates contrasts between objects, makes used materials more vivid and expressive, and allows you to adjust the shadows of objects. In addition, lighting determines the overall mood of the scene - for example, diffused light creates the effect of peace, dim lighting can cause fear, flickering light - a sense of anxiety, etc. We will familiarize you with some of the simplest techniques for adjusting lighting now, and consider more complex aspects of working with lighting in one of the next lessons.
Theoretical aspects
Setting the stage lighting involves creating light sources in it and determining their position and parameters. Light sources (like any other objects in the scene) differ in type - each of them has its own properties and scope. Work with sources is carried out in parallel with the creation of geometry objects, however, the final adjustment of their parameters is carried out in the process of creating and assigning materials, since lighting is closely related to texturing and can affect the display of materials, as well as lead to the appearance of shadows. When a scene is created, its objects are automatically lit, however, with the addition of the first light source, the default lighting is canceled. When you delete all created sources, the scene is again illuminated by the default light sources.
The main sources of light include the following (Fig. 1):
- Omni (Omnidirectional) - casts rays evenly in all directions from a single point source like a bulb without a lampshade;
- Target Spot (Spotlight Targeted) and Free Spot (Free floodlight) - they propagate rays from a point in a certain direction with a conical stream and illuminate the area inside the cone. The difference between these two sources is that the direction of the light rays in the first of them is strictly determined by the target point ( Target), and the second source does not have such a target point, and therefore the direction of the light rays in it can change as the source rotates;
- Target Directional (Target Direct) and Free Directional (Free Straight) - they propagate rays from the plane in a parallel flow in a certain direction and illuminate the area inside the straight or inclined cylinders. These sources differ in that the direction of the light rays in the first of them has a target binding, and the second is directed freely (the direction of the light rays thrown by it changes when the source rotates).
The category responsible for creating light sources Lights (Light sources) panels Create (Create), when selected, all the above types of sources become available (Fig. 2). The technology of their creation resembles the creation of geometry objects. You need to select the type of source and either just click at the point of its creation in one of the projection windows (for all sources except types Target), or drag the mouse while holding down the left button, thus indicating not only the location of the source, but also its Target-point. Created sources (as well as geometry objects) are assigned names: Omni01, Spot01, etc., which are better to replace immediately with more informative ones. Any light source can be moved, rotated and scaled in viewports in the same way as all other standard objects.
Source parameters are either set immediately when they are created in the panel Create, or change later through the panel Modify. The list of parameters is very impressive, and in this lesson we will get acquainted with only a few of them. All parameters are divided into scrolls, the main of which are the following:
- General Parameters (General parameters) - allows you to change the type of source, enable or disable the ability to generate falling shadows and exclude individual objects from the sphere of influence of the source, which is important when simulating special lighting effects (such as flashes) or when selectively illuminating one or a group of objects;
- Intensity/Color/Attenuation (Intensity / Color / Attenuation) - designed to control the intensity, color and spatial attenuation of the light flux, allows for the heterogeneity of lighting characteristic of real-world objects;
- Shadow Parameters (Shadow Options) and Shadow Map Parameters (Parameters of the shadow map) - are responsible for the nature of the generation of shadows. They allow you to adjust the sharpness of the border, change the color of the shadow, increase / decrease the distance from the object to the shadow, add a texture map to the shadow map, adjust the shadows when introducing atmospheric effects, simulate blurry shadows in foggy lighting or clear shadows created by the bright midday sun, etc. d .;
- Advanced Effects (Advanced effects) - allow you to control the clarity of the transition from source-illuminated areas of the object to unlit, enable / disable glare on the object from the light source, assign a texture map to the source, etc.
Omni Light Source
Prepare a simple scene from two objects: a plane and a ball (Fig. 3). Create a type light source Omniby opening a category Lights panels Createclick on the button with the name Omni, and then use the mouse to indicate the location of the source in one of the projection windows - an object appears that looks like an octahedron, which is a created light source. Tool Select and Move adjust the position of the source so that in the projection Front it was located to the right of the ball and was located much higher than it, and then (with the source highlighted) in the scroll General Parameters panels Modify check the box Shadows for generating shadows (Fig. 4). Render - the ball will be lit on the right and will cast a shadow (Fig. 5). Try moving the light source around the ball and you will see that one or another part of the ball will be illuminated depending on the position of the source. At the end of the experiment, return the source to its original position to the right of the ball.
Fig. 4. Initial setup of the light source Omni
Fig. 5. Ball with one Omni-source
Now we will learn to control the light intensity. To do this, with the selected light source, activate the panel Modify and in a scroll Intensity/Color/Attenuation increase the value of the parameter Multiplier (Coefficient), for example, up to 2 - the scene lighting will become much brighter (Fig. 6). In the same scroll (in the dialog box Color Selector: Light Coloropened by clicking on the field to the right of the parameter Multiplier) You can change the color of the light rays. For example, try changing the default white color, for example, to yellow - during visualization the scene will be lit with a “yellow light” (Fig. 7).
Add another Omni source to the scene and place it on the projection Front to the left of the ball, but so that it is much lower than the first source (Fig. 8). Reduce the intensity of the second source to about 0.7, and leave the color white - now the ball will be lit from two sides (Fig. 9).
Fig. 8. Adding and configuring the second Omni-source
Fig. 9. Ball with two Omni-sources
Light source Free Directional
Remove both Omni sources, which will not darken the scene, since the default light sources will turn on again. Create one type of light source Free Directional (for this it is easiest to select this type of source and click on the projection in the center of the ball Top - then the source will immediately be directed to the ball). Then move the tool as needed Select and Move and adjust its angle Select and Rotate (fig. 10). If you render, it turns out that the ball is illuminated along with a fragment of the plane, and quite intensively, while the other part of the plane is not visible at all (Fig. 11). It turns out that the brightness of the source is too high, but the coverage area of \u200b\u200bthe light flux is clearly insufficient. The situation is easy to change. First, we will figure out what parameters the coverage area of \u200b\u200bthe light flux depends on. Adjusting parameter values Hotspot/Beam (determines the size of the light cone for the inner, extremely saturated beam) and Falloff/Field (sets the size of the outer limits of the extinction of the beam to the edges) in the scroll Directional Parameters, you can change the size of the light spot emerging from the light beam and the nature of its border, which can be clear or, on the contrary, blurred. By default, the spot has a clear boundary, which is far from reality. Do Hotspot/Beam equal to 25, and Falloff/Field - 50, as a result, the spot of light will become blurred (the values \u200b\u200bof these parameters in each case will turn out to be different, it is only important that the value of the first parameter is approximately two times the value of the second) - Fig. 12. And vice versa, if the values \u200b\u200bof these parameters are close, then the boundary will be clear. As for the size of the light spot, they directly depend on the value of the parameter Hotspot/Beam - the higher it is, the larger the spot size. If desired, in this scroll, you can also change the shape of the cross section of the light cone (and hence the shape of the light spot) with a round one ( Circle) to rectangular ( Rectangle) When choosing the latter, it becomes possible to adjust the aspect ratio of the light rectangle by the parameter Aspect.
Fig. 10. Source setting Free Directional
Fig. 11. Single Source Scene Free Directional
Now expand the boundaries of lighting so that inside the light cone there is not only a ball, but also b aboutthe largest part of the plane, and do not forget that the parameter values Hotspot/Beam and Falloff/Field should vary sufficiently so that the decrease in illumination to the edges of the plane is carried out gradually. Reduce the light intensity ( Multiplier) to about 0.6 and check the box Shadows for the generation of shadows - the scene will be illuminated more naturally, although the level of illumination will be insufficient (Fig. 13). To increase the level of illumination, try to create two additional light sources (Fig. 14). For the first (whose task is to create general lighting for the scene), select the type Omni, yellow color and intensity of the order of 0.8-0.9. The purpose of the second is to provide the effect of secondary illumination arising from the reflection of incident light from light surfaces (in this case, the plane). In our example, such an effect should appear on the lower surface of the ball in the form of a certain colored flare. To simulate a similar effect, place a weak colored light source under the plane that does not cast a shadow - for example, a source of the type Free Directional. In our case, a color similar to the hue of the plane was set for it, the intensity of which is approximately 1.1, and the size is such that the plane is completely inside the boundaries of the inner light cone Hotspot/Beam. The final view of the scene is shown in Fig. fifteen.
Light Source Target Spot
Create a scene by placing a ball, a cylinder and a cube on a plane and assigning a material based on marble texture to the plane (Fig. 16). Before creating a new light source, first zoom out the scene to place the source at a sufficiently large distance from its objects. Activate in categories Lights type source Target Spotswitch to projection Front, position the mouse pointer in the upper left part of this window, left-click at this point and, without releasing the mouse, direct it to objects - a targeted spotlight will be created (Fig. 17). If you immediately render, the result will be very far from what you want (Fig. 18): the plane under the objects will be illuminated, and the objects themselves will be practically invisible.
Fig. 17. Creating a light source Target Spot
Fig. 18. Initial illumination of the scene by the source Target Spot
Let's try to change the situation and ensure that the sides of the objects facing the viewer are illuminated. As noted above, targeted light sources differ from free ones by the presence of a target ( Target) - an empty object, on which the axis of the beam of the light source is directed. Changing the features of lighting objects with a similar source is possible both by influencing the source itself and its dummy object. For example, when moving a dummy object, the light source automatically changes its orientation, but at the same time it continues to be aimed at an empty object. Try alternately using the tool Select and Move to the source and the dummy object, position the source so that the edges of the objects placed in the foreground are illuminated (Fig. 19). Visualize the scene (Fig. 20).
Fig. 19. Correction of the position of the source Target Spot
In the scroll General Parameters increase the source intensity by setting Multiplier equal to 1.25 and check the box Shadows - the scene will become brighter and the objects will now even cast shadows, though they are too dark (Fig. 21). So open the scroll Shadow Parameters (Shadow settings) and reduce the density of the shadow by setting the counter Dens (Density) equal to 0.5 - the shadows will look more natural (Fig. 22). If desired, in this scroll you can also change the color of the shadow in the field Color (Fig. 23) or make the shadow color be formed taking into account the color of the source - for this, in the menu Shadow Parameters need to enable the checkbox Light Affects Shadow Color (fig. 24).
And finally, to improve the appearance of the scene, try adding two more light sources to it: a yellow Omni source with an intensity of the order of 0.3-0.5 to create a common light background and a type source Target Spot pink color with an intensity of the order of 2 to simulate the effect of secondary lighting (Fig. 25). In addition, assign the planes a new material type Raytrace and connect the already used texture to it, trying to create an imitation of polished marble. The final view of the rendered scene is shown in Fig. 26.
Light source Free Spot
Free spotlight Free Spot different from the source just reviewed Free Directional the fact that its rays diverge not in a parallel beam, but in a conical one, like the light of real projectors, theater spotlights, flashlights, etc. Let’s try to create three such sources in order to illuminate a plane with a torus (Fig. 27) approximately in the same way as multi-colored theater spotlights could illuminate it. First, set up a weak Omni source for general lighting of the scene (Fig. 28). Then add the first free spotlight, for example with blue beams and small light cones (in this case, the parameter Hotspot/Beam equal to 10, and Falloff/Field -20) - Fig. 29. The most convenient way to create a projection spotlight Topby clicking directly on the object that it should be aimed at. As a result, the rendered scene will resemble rice. 30. In exactly the same way, create two more color spotlights (red and green) with the same parameters, and then adjust the position of all three spotlights in the projection windows, for example, as shown in Fig. 31. Check the box for each of the sources. Shadows to generate shadows and visualize the scene (Fig. 32). Because the shadows look too black, reduce their density ( Dens) in the scroll Shadow Parameters up to approximately 0.3-0.4 (Fig. 33).
Fig. 28. Adding a light source Omni
And finally, let's try to use the interesting opportunity to assign a texture map to a spotlight Projector Map (Projected map), which allows either to combine the display of the light spot with the image of an arbitrary image (if, for example, a regular photo is involved), or to modify the border of the light spot in a certain way (if a black and white image is used, playing the role of a mask). We will apply the second option and assign the textures shown in fig. 34, 35 and 36 respectively, - you need to do this in the scroll Advanced Effects (Fig. 37). A possible result of assigning texture maps is shown in Fig. 38, to achieve which the torus was additionally assigned a new material simulating plastic.
Light has three main characteristics: brightness (Multiplier), color (Color) and shadows cast from objects illuminated by it (Shadows).
When arranging light sources in a scene, be sure to pay attention to their color. Sources of daylight have a blue tint, to create a source of artificial light you need to give it a yellowish color.
It should also be taken into account that the color of the source simulating street light depends on the time of day. Therefore, if the plot of the scene involves evening time, the lighting may be in the reddish shades of summer sunset.
Various visualizers offer their own shadowing algorithms. A shadow cast from an object can say a lot - how high it is above the ground, what is the structure of the surface on which the shadow falls, what source the object is illuminated, etc.
In addition, the shadow can emphasize the contrast between the foreground and background, as well as “give out” an object that did not fall into the field of view of the lens of the virtual camera.
Depending on the shape of the shadow cast by the object, the scene may look realistic (Fig. 6.6) or not entirely believable (Fig. 6.7).
As we said above, a real ray of light undergoes a large number of reflections and refractions, so real shadows always have blurry edges. In three-dimensional graphics, a special term is used, which designates such shadows - soft shadows.
Soft shadows are hard to achieve. Many visualizers solve the problem of soft shadows by adding a non-point light source having a rectangular or other shape to the 3ds max 7 interface. Such a source emits light not from one point, but from every point on the surface. In this case, the larger the area of \u200b\u200bthe light source, the softer the shadows are obtained during visualization.
There are different approaches to rendering shadows: using a Shadow Map, Raytraced, and Global Illumination. Let's consider them in order.
Fig. 6.6. Soft shadow object
Fig. 6.7. Object with sharp shadows
Fig. 6.8. Scroll of Shadow Map Params settings
Using the shadow map allows you to get blurry shadows.
with fuzzy edges. The main Shadow Map setting is the size of the shadow map (Size parameter) in the Shadow Map Params settings rollout (Shadow map settings) (Fig. 6.8). If the map size is reduced, the clarity of the resulting shadows will also decrease.
The tracing method allows you to get perfect in shape shadows, which, however, look unnatural due to their sharp contour. Tracing is called tracking the paths of individual light rays from the light source to the camera lens, taking into account their reflection from scene objects and refraction in transparent media. The tracing method is often used to visualize scenes in which specular reflections are present.
Starting with 3ds max 5, the Area Shadows method is used to obtain soft shadows, which is based on a slightly modified tracing method. Area Shadows (Shadow Distribution) allows you to calculate the shadows from the object as if there is not one light source in the scene, but a group of point light sources evenly distributed in a certain area.
Despite the fact that the ray tracing method accurately reproduces the small details of the formed shadows, it cannot be considered an ideal solution for visualization due to the fact that the resulting shadows have sharp outlines.
The global lighting method (Radiosity) allows you to achieve soft shadows in the final image. This method is an alternative to lighting tracing. If the tracing method visualizes only those parts of the scene that are exposed to light rays, then the global lighting method calculates the light scattering in the unlit or shadowed parts of the scene based on the analysis of each image pixel. In this case, all reflections of light rays in the scene are taken into account.
Global lighting allows you to get a realistic image, but the visualization process loads the workstation very much and also requires a lot of time. Therefore, in some cases it makes sense to use a lighting system that simulates the effect of scattered light. In this case, the light sources must be placed so that their position coincides with the places of direct light. Such sources should not create shadows and should have a small brightness. With this method, of course, you do not get the same realistic image as you can get using the real global lighting method. However, in scenes that have simple geometry, it may well come in handy.
There are several algorithms for calculating global illumination; one of the methods for calculating reflected light is Photon Mapping. This method involves the calculation of global illumination, based on the creation of the so-called photon map. The photon map is scene illumination information collected by tracing.
The advantage of the photon tracing method is that once photon tracing results saved as a photon map can subsequently be used to create the effect of global illumination in three-dimensional animation scenes. The quality of global illumination calculated using photon tracing depends on the number of photons, as well as the depth of tracing. Using photon tracing, you can also calculate the caustic effect (for more details on the caustic effect, see the section “General Information on Visualization in Three-Dimensional Graphics”, Chapter 7).
