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docs/gallium/cso/velems.rst

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+.. _vertexelements:
+
+Vertex Elements
+===============
+
+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 edge flags, 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
+-------
+
+src_offset
+    The byte offset of the attribute in the buffer given by
+    vertex_buffer_index for the first vertex.
+instance_divisor
+    The instance data rate divisor, used for instancing.
+    0 means this is per-vertex data, n means per-instance data used for
+    n consecutive instances (n > 0).
+vertex_buffer_index
+    The vertex buffer this attribute lives in. Several attributes may
+    live in the same vertex buffer.
+src_format
+    The format of the attribute data. One of the PIPE_FORMAT tokens.