Use these controls to define the rendering parameters for the Grass surface in the scene, if the Grass surface channel is being used. See Grass (CineRender Surface Channel).
Render
Three render modes are available:
•Raster (8-bit): This is the default mode. Grass elements will be rendered with a maximum of 8-bit color depth. This is the fastest mode and requires the least amount of memory
•Raster (32-bit): Alternative mode.
•Ray trace: This mode can require less memory than the Raster (8-bit) mode (its memory requirements are based on the actual number of blades rendered, not the output size of the image(s)). Blades rendered using this mode will look different from blades rendered using one of the raster modes. Calculation of reflection and refraction, though, will be more precise using the Raytrace mode, and it can even be used in conjunction with GI (GI can be received only by other objects; grass itself will not affect other objects).
The Ray trace mode is slower than the raster modes and cannot render fill grass.
Sampling:
•Pixel: No interpolation will take place - each pixel will be calculated individually. This method delivers the highest quality results but also take the longest to render.
Otherwise the Pixel option should be selected in the following instances:
•If a texture in the Color channel is projected onto each individual hair.
•If the Specular Lights are too blurred, regardless of changes made to the Specular channel.
•In general, render quality will increase when very few grass segments are used.
•Vertex: The start and endpoints of segments are sampled and interpolated. This default setting offers a good compromise between quality and render time and will lead to good render results in most cases.
•Root/Tip: The root and tip are sampled and interpolated. Applying this method is the quickest for rendering (good for making test renders) but delivers the worst results. Therefore, this method is best suited for the short grass.
In the picture below: Sampling modes from left to right are Root/Tip; Vertex; Pixel. The difference is most evident when rendering long grass.
AA Quality: Use this setting to select the appropriate anti-aliasing quality. As usual, better quality will also result in longer render times.
AA Filter: Can be used to smoothly adjust antialiasing (with the AA Quality control set to Custom). Note that values greater than 100% can be entered, at which point the shadows will be rendered increasingly blurred.
Casts Shadows: Activate this setting if you want grass to cast shadows, using the following parameters.
•Transparency Threshold
•Depth Threshold
•Antialiasing
•Filter
•Sample Size
•Shadow map
•Resolution
Tracing Memory: When the Ray Trace render mode is applied, various amounts of memory can be allotted. As usual, the more memory allotted, the faster the rendering will be (within limits: if memory must be allotted from the hard drive, rendering will slow accordingly).