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| -rw-r--r-- | src/gallium/docs/source/cso/velems.rst | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/src/gallium/docs/source/cso/velems.rst b/src/gallium/docs/source/cso/velems.rst index 92cde014fb8..978ad4a2434 100644 --- a/src/gallium/docs/source/cso/velems.rst +++ b/src/gallium/docs/source/cso/velems.rst @@ -3,9 +3,44 @@ Vertex Elements =============== -This state controls format etc. of the input attributes contained -in the pipe_vertex_buffer(s). There's one pipe_vertex_element array member -for each input attribute. +This state controls the format of the input attributes contained in +pipe_vertex_buffers. There is one pipe_vertex_element array member for each +input attribute. + +Input Formats +------------- + +Gallium supports a diverse range of formats for vertex data. Drivers are +guaranteed to support 32-bit floating-point vectors of one to four components. +Additionally, they may support the following formats: + +* Integers, signed or unsigned, normalized or non-normalized, 8, 16, or 32 + bits wide +* Floating-point, 16, 32, or 64 bits wide + +At this time, support for varied vertex data formats is limited by driver +deficiencies. It is planned to support a single uniform set of formats for all +Gallium drivers at some point. + +Rather than attempt to specify every small nuance of behavior, Gallium uses a +very simple set of rules for padding out unspecified components. If an input +uses less than four components, it will be padded out with the constant vector +``(0, 0, 0, 1)``. + +Fog, point size, the facing bit, and edgeflags, all are in the standard format +of ``(x, 0, 0, 1)``, and so only the first component of those inputs is used. + +Position +%%%%%%%% + +Vertex position may be specified with two to four components. Using less than +two components is not allowed. + +Colors +%%%%%% + +Colors, both front- and back-facing, may omit the alpha component, only using +three components. Using less than three components is not allowed. Members ------- |