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