Specify An Exact Color

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First, you'll need to know the depth of the color buffer you are rendering to. For an RGB color buffer, you can obtain these values with the following code:

  GLint redBits, greenBits, blueBits;

  glGetIntegerv (GL_RED_BITS, &redBits);
  glGetIntegerv (GL_GREEN_BITS, &greenBits);
  glGetIntegerv (GL_BLUE_BITS, &blueBits);

If the depth value for each component is at least as large as your required color precision, you can specify an exact color for your primitives. Specify the color you want to use into the most significant bits of three unsigned integers and use glColor3ui() to specify the color.

If your color buffer isn't deep enough to accurately represent the color you desire, you'll need a fallback strategy. Trimming off the least significant bits of each color component is an acceptable alternative. Again, use glColor3ui() (or glColor3us(), etc.) to specify the color with your values stored in the most significant bits of each parameter.

In either event, you'll need to ensure that any state that could affect the final color has been disabled. The following code will accomplish this:

  glDisable (GL_BLEND);
  glDisable (GL_DITHER);
  glDisable (GL_FOG);
  glDisable (GL_LIGHTING);
  glDisable (GL_TEXTURE_1D);
  glDisable (GL_TEXTURE_2D);
  glDisable (GL_TEXTURE_3D);
  glShadeModel (GL_FLAT);