| | '''OpenGL extension ARB.enhanced_layouts |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.ARB.enhanced_layouts to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | This extension adds the following functionality to layout qualifiers, |
| | including broadening the API where this functionality is reflected. |
| | |
| | The following are added: |
| | |
| | 1) Use compile-time constant expressions. E.g., |
| | |
| | const int start = 6; |
| | layout(location = start + 2) int vec4 v; |
| | |
| | 2) Specify explicit byte offsets within a uniform or shader storage block. |
| | For example, if you want two vec4 variables "batman" and "robin" to |
| | appear at byte offsets 0 and 64 in your block, you can say: |
| | |
| | uniform Block { |
| | layout(offset = 0) vec4 batman; |
| | layout(offset = 64) vec4 robin; |
| | }; |
| | |
| | 3) Force alignment within a uniform or shader storage block. The previous |
| | example could also be expressed: |
| | |
| | uniform Block { |
| | vec4 batman; |
| | layout(align = 64) vec4 robin; |
| | }; |
| | |
| | This says the member 'robin' must start at the next address that is a |
| | multiple of 64. It allows constructing the same layout in C and in GLSL |
| | without inventing explicit offsets. |
| | |
| | Explicit offsets and aligned offsets can be combined: |
| | |
| | uniform Block { |
| | vec4 batman; |
| | layout(offset = 44, align = 8) vec4 robin; |
| | }; |
| | |
| | would make 'robin' be at the first 8-byte aligned address, starting at |
| | 44, which is 48. This is more useful when using the *align* at |
| | the block level, which will apply to all members. |
| | |
| | 4) Specify component numbers to more fully utilize the vec4-slot interfaces |
| | between shader outputs and shader inputs. |
| | |
| | For example, you could fit the following |
| | |
| | - an array of 32 vec3 |
| | - a single float |
| | |
| | into the space of 32 vec4 slots using the following code: |
| | |
| | // consume X/Y/Z components of 32 vectors |
| | layout(location = 0) in vec3 batman[32]; |
| | |
| | // consumes W component of first vector |
| | layout(location = 0, component = 3) in float robin; |
| | |
| | Further, an array of vec3 and an array of float can be stored |
| | interleaved, using the following. |
| | |
| | // consumes W component of 32 vectors |
| | layout(location = 0, component = 3) in float robin[32]; |
| | |
| | // consume X/Y/Z components of 32 vectors |
| | layout(location = 0) in vec3 batman[32]; |
| | |
| | 5) Specify transform/feedback buffers, locations, and widths. For example: |
| | |
| | layout(xfb_buffer = 0, xfb_offset = 0) out vec3 var1; |
| | layout(xfb_buffer = 0, xfb_offset = 24) out vec3 var2; |
| | layout(xfb_buffer = 1, xfb_offset = 0) out vec4 var3; |
| | |
| | The second line above says to write var2 out to byte offset 24 of |
| | transform/feedback buffer 0. (When doing this, output are only |
| | captured when xfb_offset is used.) |
| | |
| | To specify the total number of bytes per entry in a buffer: |
| | |
| | layout(xfb_buffer = 1, xfb_stride = 32) out; |
| | |
| | This is necessary if, say, var3 above, which uses bytes 0-11, |
| | does not fully fill the buffer, which in this case takes 32 bytes. |
| | |
| | Use of this feature effectively eliminates the need to use previously |
| | existing API commands to describe the transform feedback layout. |
| | |
| | 6) Allow locations on input and output blocks for SSO interface matching. |
| | |
| | For example: |
| | |
| | layout(location = 4) in block { |
| | vec4 batman; // gets location 4 |
| | vec4 robin; // gets location 5 |
| | layout(location = 7) vec4 joker; // gets location 7 |
| | vec4 riddler; // location 8 |
| | }; |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/ARB/enhanced_layouts.txt |
| | ''' |
| | from OpenGL import platform, constant, arrays |
| | from OpenGL import extensions, wrapper |
| | import ctypes |
| | from OpenGL.raw.GL import _types, _glgets |
| | from OpenGL.raw.GL.ARB.enhanced_layouts import * |
| | from OpenGL.raw.GL.ARB.enhanced_layouts import _EXTENSION_NAME |
| |
|
| | def glInitEnhancedLayoutsARB(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
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| |
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| | |
