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"""Transliteration of https://open.gl/feedback into Python"""
from __future__ import print_function
import pygamegltest
from OpenGL._bytes import as_8_bit
from OpenGL.GL import *
from OpenGL.GL import shaders
vertex_shader = """#version 150 core
in float inValue;
out float geoValue;
uniform float junk; // Just here for the introspection test
void main() {
geoValue = sqrt(inValue) + junk;
}
"""
geometry_shader = """#version 150 core
layout(points) in;
layout(triangle_strip, max_vertices = 3) out;
in float[] geoValue;
out float outValue;
void main() {
for (int i = 0; i < 3; i++) {
outValue = geoValue[0] + i;
EmitVertex();
}
EndPrimitive();
}
"""
@pygamegltest.pygametest(name="Geometry Shader Test")
def main():
program = shaders.compileProgram(
shaders.compileShader([vertex_shader], GL_VERTEX_SHADER),
shaders.compileShader([geometry_shader], GL_GEOMETRY_SHADER)
)
# test that we can describe the attributes in the shader
for i in range( glGetProgramiv( program, GL_ACTIVE_ATTRIBUTES )):
name,size,type = glGetActiveAttrib( program, i )
print( 'Arribute %s(%i) -> %s %s'%(name,i,size,type))
length,size,type,name = GLsizei(),GLint(),GLenum(),(GLchar*8)()
glGetActiveAttrib( program, i, None, length,size,type,name )
assert length.value == len(name.value),(length.value,name.value)
assert type.value == 5126, type.value
for i in range( glGetProgramiv( program, GL_ACTIVE_UNIFORMS )):
name,size,type = glGetActiveUniform( program, i )
print( 'Uniform %s(%i) -> %s %s'%(name,i,size,type))
length,size,type,name = GLsizei(),GLint(),GLenum(),(GLchar*5)()
glGetActiveUniform( program, i, 5, length, size, type, name )
assert length.value == len(name.value),(length.value,name.value)
assert type.value == 5126, type.value
buff = (ctypes.c_char_p * 1)( as_8_bit("outValue\000") )
c_text = ctypes.cast(ctypes.pointer(buff), ctypes.POINTER(ctypes.POINTER(GLchar)))
# modifies the state in the linking of the program
glTransformFeedbackVaryings(program, 1, c_text, GL_INTERLEAVED_ATTRIBS);
# so have to re-link
glLinkProgram(program)
glUseProgram(program);
vao = glGenVertexArrays(1);
glBindVertexArray(vao);
data = (GLfloat * 5)(1.0, 2.0, 3.0, 4.0, 5.0)
vbo = glGenBuffers(1);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, ctypes.sizeof(data), data, GL_STATIC_DRAW);
inputAttrib = glGetAttribLocation(program, "inValue");
glEnableVertexAttribArray(inputAttrib);
glVertexAttribPointer(inputAttrib, 1, GL_FLOAT, GL_FALSE, 0, 0);
tbo = glGenBuffers(1);
glBindBuffer(GL_ARRAY_BUFFER, tbo);
glBufferData(GL_ARRAY_BUFFER, ctypes.sizeof(data) * 3, None, GL_STATIC_READ);
glEnable(GL_RASTERIZER_DISCARD);
glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, tbo);
glBeginTransformFeedback(GL_TRIANGLES);
glDrawArrays(GL_POINTS, 0, 5);
glEndTransformFeedback();
glDisable(GL_RASTERIZER_DISCARD);
glFlush();
feedback = (GLfloat*15)(*([0]*15))
glGetBufferSubData(GL_TRANSFORM_FEEDBACK_BUFFER, 0, ctypes.sizeof(feedback), feedback);
for value in feedback:
print(value)
if __name__ == "__main__":
main()
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