PyOpenGL - passing transformation matrix into shader
- by M-V
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?
