PyOpenGL - passing transformation matrix into shader
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M-V
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Published on 2012-10-06T09:36:05Z
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2012/10/06
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I am having trouble passing projection and modelview matrices into the GLSL shader from my PyOpenGL code. My understanding is that OpenGL matrices are column major, but when I pass in projection and modelview matrices as shown, I don't see anything. I tried the transpose of the matrices, and it worked for the modelview matrix, but the projection matrix doesn't work either way. Here is the code:
import OpenGL from OpenGL.GL import * from OpenGL.GL.shaders import * from OpenGL.GLU import * from OpenGL.GLUT import * from OpenGL.GLUT.freeglut import * from OpenGL.arrays import vbo import numpy, math, sys strVS = """ attribute vec3 aVert; uniform mat4 uMVMatrix; uniform mat4 uPMatrix; uniform vec4 uColor; varying vec4 vCol; void main() { // option #1 - fails gl_Position = uPMatrix * uMVMatrix * vec4(aVert, 1.0); // option #2 - works gl_Position = vec4(aVert, 1.0); // set color vCol = vec4(uColor.rgb, 1.0); } """ strFS = """ varying vec4 vCol; void main() { // use vertex color gl_FragColor = vCol; } """ # particle system class class Scene: # initialization def __init__(self): # create shader self.program = compileProgram(compileShader(strVS, GL_VERTEX_SHADER), compileShader(strFS, GL_FRAGMENT_SHADER)) glUseProgram(self.program) self.pMatrixUniform = glGetUniformLocation(self.program, 'uPMatrix') self.mvMatrixUniform = glGetUniformLocation(self.program, "uMVMatrix") self.colorU = glGetUniformLocation(self.program, "uColor") # attributes self.vertIndex = glGetAttribLocation(self.program, "aVert") # color self.col0 = [1.0, 1.0, 0.0, 1.0] # define quad vertices s = 0.2 quadV = [ -s, s, 0.0, -s, -s, 0.0, s, s, 0.0, s, s, 0.0, -s, -s, 0.0, s, -s, 0.0 ] # vertices self.vertexBuffer = glGenBuffers(1) glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer) vertexData = numpy.array(quadV, numpy.float32) glBufferData(GL_ARRAY_BUFFER, 4*len(vertexData), vertexData, GL_STATIC_DRAW) # render def render(self, pMatrix, mvMatrix): # use shader glUseProgram(self.program) # set proj matrix glUniformMatrix4fv(self.pMatrixUniform, 1, GL_FALSE, pMatrix) # set modelview matrix glUniformMatrix4fv(self.mvMatrixUniform, 1, GL_FALSE, mvMatrix) # set color glUniform4fv(self.colorU, 1, self.col0) #enable arrays glEnableVertexAttribArray(self.vertIndex) # set buffers glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer) glVertexAttribPointer(self.vertIndex, 3, GL_FLOAT, GL_FALSE, 0, None) # draw glDrawArrays(GL_TRIANGLES, 0, 6) # disable arrays glDisableVertexAttribArray(self.vertIndex) class Renderer: def __init__(self): pass def reshape(self, width, height): self.width = width self.height = height self.aspect = width/float(height) glViewport(0, 0, self.width, self.height) glEnable(GL_DEPTH_TEST) glDisable(GL_CULL_FACE) glClearColor(0.8, 0.8, 0.8,1.0) glutPostRedisplay() def keyPressed(self, *args): sys.exit() def draw(self): glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) # build projection matrix fov = math.radians(45.0) f = 1.0/math.tan(fov/2.0) zN, zF = (0.1, 100.0) a = self.aspect pMatrix = numpy.array([f/a, 0.0, 0.0, 0.0, 0.0, f, 0.0, 0.0, 0.0, 0.0, (zF+zN)/(zN-zF), -1.0, 0.0, 0.0, 2.0*zF*zN/(zN-zF), 0.0], numpy.float32) # modelview matrix mvMatrix = numpy.array([1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.5, 0.0, -5.0, 1.0], numpy.float32) # render self.scene.render(pMatrix, mvMatrix) # swap buffers glutSwapBuffers() def run(self): glutInitDisplayMode(GLUT_RGBA) glutInitWindowSize(400, 400) self.window = glutCreateWindow("Minimal") glutReshapeFunc(self.reshape) glutDisplayFunc(self.draw) glutKeyboardFunc(self.keyPressed) # Checks for key strokes self.scene = Scene() glutMainLoop() glutInit(sys.argv) prog = Renderer() prog.run()
When I use option #2
in the shader without either matrix, I get the following output:
What am I doing wrong?
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