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I have written a code to render a triangle using a shader program. I want to rotate the triangle. I'm using PyGLM to set a transformation matrix. Here I'm presenting the whole code. If I run this code a triangle is appearing in the window as expected, but there is no rotation. I think I've failed to pass the transformation matrix to the buffer.

from OpenGL.GL import * from OpenGL.GLU import * from OpenGL.GLUT import * from OpenGL.GL import shaders import numpy as np import glm VERTEX_SHADER = """ #version 330 in vec4 position; in vec3 color; out vec3 newColor; void main() { gl_Position = position; newColor = color; } """ FRAGMENT_SHADER = """ #version 330 in vec3 newColor; out vec4 outColor; void main() { outColor = vec4(newColor,1.0f); } """ shaderProgram = None def initliaze(): global VERTEXT_SHADER global FRAGMEN_SHADER global shaderProgram vertexshader = shaders.compileShader(VERTEX_SHADER, GL_VERTEX_SHADER) fragmentshader = shaders.compileShader(FRAGMENT_SHADER, GL_FRAGMENT_SHADER) shaderProgram = shaders.compileProgram(vertexshader, fragmentshader) triangles = [-0.5, -0.5, 0.0, 1.0,0.0,0.0, 0.5, -0.5, 0.0, 0.0,1.0,0.0, 0.0, 0.5, 0.0, 0,0,0.0,1.0] triangles = np.array(triangles, dtype=np.float32) VBO = glGenBuffers(1) glBindBuffer(GL_ARRAY_BUFFER, VBO) glBufferData(GL_ARRAY_BUFFER, triangles.nbytes, triangles, GL_DYNAMIC_DRAW) position = glGetAttribLocation(shaderProgram, 'position') glVertexAttribPointer(position, 3, GL_FLOAT, GL_FALSE, 24, ctypes.c_void_p(0)) glEnableVertexAttribArray(position) color = glGetAttribLocation(shaderProgram, 'color') glVertexAttribPointer(color, 3, GL_FLOAT, GL_FALSE, 24, ctypes.c_void_p(12)) glEnableVertexAttribArray(color) def render(): global shaderProgram global angle #shader glUseProgram(shaderProgram) glClearColor(0, 0, 0, 1) glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) #transform matrix transform = glm.mat4(1) transform = glm.translate(transform, glm.vec3(0.5,-0.5,0.0)) transform = glm.rotate(transform, glutGet(GLUT_ELAPSED_TIME),glm.vec3(0,0,1)) transformLoc = glGetUniformLocation(shaderProgram,"transform") glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm.value_ptr(transform)) #render program glDrawArrays(GL_TRIANGLES, 0, 3) glUseProgram(0) glutSwapBuffers() def main(): glutInit([]) glutInitWindowSize(640, 480) glutCreateWindow("pyopengl with glut 2") initliaze() glutDisplayFunc(render) glutMainLoop() if __name__ == '__main__': main()
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    Have you already checked a tutorial like this? Commented Aug 8, 2020 at 12:18
  • yes... but couldn't apply the concept for python. Commented Aug 8, 2020 at 13:59

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In VERTEX_SHADER you didn't mentioned transform variable. So your triangle position remain fixed after you run the program. Change your VERTEX_SHADER as following.

VERTEX_SHADER = """ #version 330 in vec4 position; in vec3 color; out vec3 newColor; uniform mat4 transform; void main() { gl_Position = transform*position; newColor = color; } """

In your code you are accessing the location of location of a uniform variable transform by following line.

transformLoc = glGetUniformLocation(shaderProgram,"transform")

You should add glutPostRedisplay() function after the glutSwapBuffers() function to visualize the continuous change.

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Looks like you will want to create your own library from GLM. What you're doing in the code above no longer works. As another user stated, this is a good template to build functionality from. I'd suggest downloading GLM, taking it apart, and reverse engineering what you need into Python.

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I checked this before... but couldn't apply the concept for python. I'm missing something, I don't know.
You... can't reverse engineer GLM? Why not? All you need to do is download GLM and look at the .hpp files, and translate them into Python. Some of the math functions can be handled with NumPy.
I've updated the complete code. Still I'm confused how to do it.

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