When a large part of the texture corresponds to a single pixel in the framebuffer, simple filtering may give strong aliasing artefacts.  In animations, scintillation (shimmering) artefacts may also appear.



Would prefer to average texels over a large area of the texture.  One possible way to do this is to form smaller texture maps by averaging groups of texels.  Mipmapping provides a simple way to do this.

High

Exercise
Your colleague is trying to texture map a ground plane with a mipmapped, repeating texture in s and t.  However, it’s not working as expected!

1. What is wrong with the following code?  Hint:  there may be multiple errors.

m_tTexture.SetSamplerObjectParameter(GL_TEXTURE_MIN_FILTER, GL_LINEAR);
m_tTexture.SetSamplerObjectParameter(GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR);
m_tTexture.SetSamplerObjectParameter(GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
m_tTexture.SetSamplerObjectParameter(GL_TEXTURE_WRAP_T, GL_REPEAT);

• The minification filter should be GL_LINEAR_MIPMAP_LINEAR
• The magnification filter should be GL_LINEAR
• GL_REPEAT should be used for the s wrapping mode

2. What other things might your colleague want to check?

• The texture is loaded
• When the texture is loaded, it is mipmapped
• Texture coordinates are correct
• Texture coordinates are read in vertex shader and passed to fragment shader
• When rendering, texture is bound
• Sampler in fragment shader is using the correct texture unit
• In fragment shader, texture is being used (e.g., bUseTexture = true in template)