INSIDE 3DS MAX® 7 [Electronic resources] نسخه متنی

Assign Vertex Colors Utility

The Radiosity renderer realistically imitates the way lights interact with an environment. For example, if a white object is in a room with blue walls and an orange ceiling, then the white object will appear somewhat orange on top and blue on its sides, as a result of light bouncing off the colored walls and ceiling. But radiosity, though very desirable, has always come with its own set of problems and limitations.

Rendering with radiosity is relatively quick per rendered framebut before any frame is rendered, a radiosity solution has to be calculated for the entire scene, and that can take quite a long time, depending on the complexity of the scene. Also, using radiosity requires you to keep your objects strictly in placeno animationafter a radiosity solution is generated; if you don't, you will get chaotic, unusable textures. You can get around this by enabling Regather Indirect Illumination from the Rendering Parameters rollout, but as this generates a new radiosity solution for each frame, the entire scene will take much longer to render.

Using Assign Vertex Colors, you have the flexibility to animate after the fact without causing rendering problems or taking a huge render hit. Unfortunately, since mental ray does not work with Vertex Color assignment, your only option is the Default Scanline Renderer.

Note

Vertex Colors can be assigned to either the faces or the vertices. Using the Color by Face method is less accurate but calculates faster. Using the Color by Vertex method uses each vertex of the faces, so it is more accurate and slower to calculate.

The basic workflow is as follows:

Radiosity is generated from the Render Scene dialog, within the Advanced Lighting tab. The Start button calculates the lighting in the scene and generates a solution. The time needed for the calculation will vary based on the size of the scene, the number of lights, and the level of accuracy you specify in the Initial Quality parameter.

After the radiosity solution has been generated, the next step is to access the Assign Vertex Colors utility from the Tools menu > Utility panel.

In the previous version of 3ds max, final gathering would automatically be calculated into the vertex colors and the option to omit this was unavailable. New to 3ds max 7 is the option Radiosity, Reuse Direct Illumination from Solution, which will calculate faster but omit the final gathering. (You will need to select the option Radiosity, Render Direct Illumination, if final gathering was used to generate the solution and you want it to be calculated into the vertex colors.) By omitting the final gathering, you will get lower quality but faster calculation. Clicking the Assign to Selected button bakes the radiosity solution to the vertex colors of the selected object (Figure 5.17).

After vertex colors are assigned, a VertexPaint modifier appears in the modifier stack of your selected object. This allows you to edit the vertex colors. Once you are satisfied with the vertex colors, add a Vertex Color Map in the Diffuse Color slot of your object's material and render the scene.

You can also now assign vertex colors from the VertexPaint modifier using the same methods as in the Assign Vertex Colors utility (Figure 5.18).

Blurring the vertex colors is possible from the Vertex Colors modifiers. Blurring colors may smooth out some unwanted banding or over-sharp color edges, but too much blur will cause unwanted smearing in areas that need to be sharp. Blur only once or twice in areas that need to be smoother (Figure 5.19).