MAT Common Page
The MAT Common Page allows you adjust many rendering settings. These settings are completely independent of the shader being used, so they be applied to any shader. Some MATs may require certain rendering features be enabled or disabled to work correctly, in that case the parameters will be disabled for that MAT type.
Blending is summing the color value of the pixel being drawn and the pixel currently present in the Color-Buffer. Blending is typically used to simulate Transparency.
The blending equation is:
Final Pixel Value = (Source Blend * Source Color) + (Dest Blend * Destination Color)
blending - This toggle enables and disables blending. However see the wiki article Transparency.
srcblend - This value is multiplied by the color value of the pixel that is being written to the Color-Buffer (also know as the Source Color).
destblend - This value is multiplied by the color value of the pixel currently in the Color-Buffer (also known as the Destination Color).
Separate Alpha Function
separatealphafunc - This toggle enables and disables separate blending options for the alpha values.
srcblend - This value is multiplied by the alpha value of the pixel that is being written to the Color-Buffer (also know as the Source Alpha).
destblend - This value is multiplied by the alpha value of the pixel currently in the Color-Buffer (also known as the Destination Alpha).
Depth-Testing is comparing the depth value of the pixel being drawn with the pixel currently in the Frame-Buffer. A pixel that is determined to be in-front of the pixel currently in the Frame-Buffer will be drawn over it. Pixels that are determined to be behind the pixel currently in the Frame-Buffer will not be drawn. Depth-Testing allows geometry in a 3D scene to occlude geometry behind it, and be occluded by geometry in-front of it regardless of the order the geometry was drawn.
For a more detailed description of Depth-Testing, refer to the Depth-Test article.
depthtest - Enables and disables the Depth-Test. If the depth-test is disabled, depths values aren't written to the Depth-Buffer.
Depth Test Function
depthfunc - The depth value of the pixel being drawn is compared to the depth value currently in the depth-buffer using this function. If the test passes then the pixel is drawn to the Frame-Buffer. If the test fails the pixel is discarded and no changes are made to the Frame-Buffer.
Write Depth Values
depthwriting - If Write Depth Values is on, pixels that pass the depth-test will write their depth value to the Depth-Buffer. If this isn't on then no changes will be made to the Depth-Buffer, regardless of if the pixels drawn pass or fail the depth-test.
Alpha-testing allows you to choose to draw or not draw a pixel based on its alpha value.
Discard Pixels Based On Alpha
alphatest - This enables or disables the pixel alpha test.
Keep Pixels with Alpha
alphatest - This menu works in conjunction with the Alpha Threshold parameter below in determining which pixels to keep based on their alpha value.
alphathreshold - This value is what the pixel's alpha is compared to to determine if the pixel should be drawn. Pixels with alpha greater than the Alpha Threshold will be drawn. Pixels with alpha less than or equal to the Alpha Threshold will not be drawn.
The wire-frame feature will render the geometry as wire-frame, using the actual primitive type used in the render. What this means is surfaces like Metaballs, NURBs and Beziers will become a wire-frame of the triangles/triangle-strips used to render them (since these types of primitives can't be natively rendered in OpenGL).
wireframe - Enables and disables wire-frame rendering with the option of OpenGL Tesselated or Topology based wireframes.
wirewidth - This value is the width that the wires will be. This value is in pixels.
The cull face parameter will cull faces from the render output. This can be used as an optimization or sometimes to remove artifacts. See Back-Face Culling for more infomation.
cullface - Selects which faces to render.
- Use Render Setting - use the render settings found in the Render or Render Pass TOP.
- Neither - do not cull any faces, render everything.
- Back Faces - cull back faces, render front faces.
- Front Faces - cull front faces, render back faces.
- Both Faces - cull both faces, render nothing.
Polygon Depth Offset
This feature pushes the polygons back into space a tiny fraction. This is useful when you are rendering two polygons directly on-top of each other and are experiencing Z-Fighting. Refer to Polygon Depth Offset for more information. This is also an important feature when doing shadows.
Polygon Depth Offset
polygonoffset - Turns on the polygon offset feature.
polygonoffsetfactor - Adds an offset to the Z value that depends on how sloped the surface is to the viewer.
polygonoffsetunits - Adds a constant offset to the Z value.