CSCI 441 - Computer Graphics

Things to check:

• Vertex positions use a 1.0 for their w component of the vec4.
• Check the winding order of your vertices. If back face culling is enabled, then you may be winding in the reverse order.
• Did it get translated out of view?
• If drawing in 2D, did it rotate out of the image plane? What is your axis of rotation?
• If you are using a scale matrix, then what should the scale factor be to have no scaling take place? (We want the initial value to remain constant)
• Check the order of your transformations. Always multiply matrix * vector.
• Is your camera in the correct place? Is the near clip plane non-zero? Is the object beyond your far clip plane? Is the camera pointing the right direction?
• Is there an error with your shader program?
• Are all your calculations performed in the same coordinate space?

Things to check:

• There will be a log message after the shader that failed to compile. Common reasons:
  • Attempting to multiply a mat4 * vec3 or a mat3 * vec4.
  • A variable or function doesn't exist.

Things to check:

• There will be a log message after the shaders are compiled.Common reasons:
  • Do the input varyings exist as output varyings in the prior shader stage?

Things to check:

• Did your shader program compile?
• Is the shader program ready for use when rendering? Do you have VAO bound, a Shader Program in use, textures bound, uniforms set?
• Is your camera in the correct place? Is the near clip plane non-zero? Is the object beyond your far clip plane? Is the camera pointing the right direction?