OpenGL Programming/Migrating from 1.x to 2.x

OpenGL ES 2.0 has most of OpenGL 1.x just not available, and OpenGL 3.x and OpenGL 4.x deprecate it (the feature are still available in the "compatibility profile", but you can expect the features to disappear soon enough).

However, little is said about how these features are replaced in the new versions. Here's how:

Matrix stackEdit

Deprecated functions: glIdentity, glRotate, glOrtho, gluOrtho...

Matrix maths can be done:

GLM provides glm::ortho to replace glOrtho and gluOrtho for orthographic perspectives (and 2D programming).

Examples:

Vertex and textureEdit

Deprecated functions: glVertex, glTexCoord...

These data are now sent in batch mode, as C arrays. You can use:

  • directly a C array : data is resent a each frame
  • glBufferData : send the C data once to the graphic card, then refer to the buffer

You use glVertexAttribPointer, once time for each vertex attribute (position, color, texture coordinate...), passing it the C array or OpenGL buffer.

Examples:

Then you use glDrawArrays or glDrawElements to start drawing.

NormalsEdit

Deprecated functions: glNormal, glNormalPointer

Normals need to be passed to the shaders (namely for shading computations), like vector coordinates (glVertexAttribPointer). To compute the normal of 3 vertices a, b and c in counter-clockwise order, GLM provides:

glm::normalize(glm::cross(b - a, c - a));
glm::fastNormalize(glm::cross(b - a, c - a));  // faster but less accurate

Examples:

Evaluators - Bezier curves and surfacesEdit

Deprecated functions: glMap1, glMap2, glEvalCoord, glEvalPoint...

  • GLU ES - http://code.google.com/p/glues/ - this is for OpenGL 1.x, so it may not work in a 2.x environment, but provides replacement code
  • Manual code (not that hard)

Examples:

LightingEdit

Deprecated functions: glLight (glLightfv3, etc.), glShadeModel...

The bad news is that you have to reimplement everything in the shaders. The good news is that it's not so hard, plus you have copy/pasteable code in the examples below :)

You also need to make the light parameters available to your shaders, and it's best to store them as a shader struct.

Examples:

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Last modified on 12 August 2012, at 09:49