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'''OpenGL extension NV.geometry_shader_passthrough
This module customises the behaviour of the
OpenGL.raw.GL.NV.geometry_shader_passthrough to provide a more
Python-friendly API
Overview (from the spec)
Geometry shaders provide the ability for applications to process each
primitive sent through the GL using a programmable shader. While geometry
shaders can be used to perform a number of different operations, including
subdividing primitives and changing primitive type, one common use case
treats geometry shaders as largely "passthrough". In this use case, the
bulk of the geometry shader code simply copies inputs from each vertex of
the input primitive to corresponding outputs in the vertices of the output
primitive. Such shaders might also compute values for additional built-in
or user-defined per-primitive attributes (e.g., gl_Layer) to be assigned
to all the vertices of the output primitive.
This extension provides a shading language abstraction to express such
shaders without requiring explicit logic to manually copy attributes from
input vertices to output vertices. For example, consider the following
simple geometry shader in unextended OpenGL:
layout(triangles) in;
layout(triangle_strip) out;
layout(max_vertices=3) out;
in Inputs {
vec2 texcoord;
vec4 baseColor;
} v_in[];
out Outputs {
vec2 texcoord;
vec4 baseColor;
};
void main()
{
int layer = compute_layer();
for (int i = 0; i < 3; i++) {
gl_Position = gl_in[i].gl_Position;
texcoord = v_in[i].texcoord;
baseColor = v_in[i].baseColor;
gl_Layer = layer;
EmitVertex();
}
}
In this shader, the inputs "gl_Position", "Inputs.texcoord", and
"Inputs.baseColor" are simply copied from the input vertex to the
corresponding output vertex. The only "interesting" work done by the
geometry shader is computing and emitting a gl_Layer value for the
primitive.
The following geometry shader, using this extension, is equivalent:
#extension GL_NV_geometry_shader_passthrough : require
layout(triangles) in;
// No output primitive layout qualifiers required.
// Redeclare gl_PerVertex to pass through "gl_Position".
layout(passthrough) in gl_PerVertex {
vec4 gl_Position;
} gl_in[];
// Declare "Inputs" with "passthrough" to automatically copy members.
layout(passthrough) in Inputs {
vec2 texcoord;
vec4 baseColor;
} v_in[];
// No output block declaration required.
void main()
{
// The shader simply computes and writes gl_Layer. We don't
// loop over three vertices or call EmitVertex().
gl_Layer = compute_layer();
}
The official definition of this extension is available here:
http://www.opengl.org/registry/specs/NV/geometry_shader_passthrough.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.NV.geometry_shader_passthrough import *
from OpenGL.raw.GL.NV.geometry_shader_passthrough import _EXTENSION_NAME
def glInitGeometryShaderPassthroughNV():
'''Return boolean indicating whether this extension is available'''
from OpenGL import extensions
return extensions.hasGLExtension( _EXTENSION_NAME )
### END AUTOGENERATED SECTION
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