1.. _vertexelements: 2 3Vertex Elements 4=============== 5 6This state controls the format of the input attributes contained in 7pipe_vertex_buffers. There is one pipe_vertex_element array member for each 8input attribute. 9 10Input Formats 11------------- 12 13Gallium supports a diverse range of formats for vertex data. Drivers are 14guaranteed to support 32-bit floating-point vectors of one to four components. 15Additionally, they may support the following formats: 16 17* Integers, signed or unsigned, normalized or non-normalized, 8, 16, or 32 18 bits wide 19* Floating-point, 16, 32, or 64 bits wide 20 21At this time, support for varied vertex data formats is limited by driver 22deficiencies. It is planned to support a single uniform set of formats for all 23Gallium drivers at some point. 24 25Rather than attempt to specify every small nuance of behavior, Gallium uses a 26very simple set of rules for padding out unspecified components. If an input 27uses less than four components, it will be padded out with the constant vector 28``(0, 0, 0, 1)``. 29 30Fog, point size, the facing bit, and edgeflags, all are in the standard format 31of ``(x, 0, 0, 1)``, and so only the first component of those inputs is used. 32 33Position 34%%%%%%%% 35 36Vertex position may be specified with two to four components. Using less than 37two components is not allowed. 38 39Colors 40%%%%%% 41 42Colors, both front- and back-facing, may omit the alpha component, only using 43three components. Using less than three components is not allowed. 44 45Members 46------- 47 48src_offset 49 The byte offset of the attribute in the buffer given by 50 vertex_buffer_index for the first vertex. 51instance_divisor 52 The instance data rate divisor, used for instancing. 53 0 means this is per-vertex data, n means per-instance data used for 54 n consecutive instances (n > 0). 55vertex_buffer_index 56 The vertex buffer this attribute lives in. Several attributes may 57 live in the same vertex buffer. 58src_format 59 The format of the attribute data. One of the PIPE_FORMAT tokens. 60