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3D OpenGL Programming Insights from Quake 2 Model Files

Dive deeper into the world of 3D OpenGL programming using model files and textures from Quake 2. Learn about vertices, triangles, texture coordinates, lighting, and more. Get practical tips and code snippets for creating immersive 3D graphics.

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3D OpenGL Programming Insights from Quake 2 Model Files

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  1. A Bit More on OpenGL Matt Wronkiewicz Be Users Group at UIUC

  2. Introduction • This presentation will cover 3D OpenGL programming as seen in Quake 2. • Model files: MD2 for models and PCX for textures.

  3. Model Files • Files contain vertices, triangles, and texture coordinates. • Vertices are groups of three floats • Triangles are groups of three vertices. • Vertices used by more than one triangle are only listed once. • Code for reading model files available from ftp.idsoftware.com

  4. Textures • Texture coordinates contained in model file. • Textures are in PCX image files. • Texture size must be a power of 2 (use gluScaleImage()). • Automatically mapped to drawn triangles.

  5. Texture Settings glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); glTexParameteri(GL_TEXTURE_2D. GL_TEXTURE_WRAP_T, GL_CLAMP); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

  6. Setting up OpenGL for 3D Drawing • glEnable() sets flags in OpenGL • GL_CULL_FACE • GL_TEXTURE_2D • Set drawing mode with glPolygonMode(GL_FRONT, GL_FILL). • Set view with glOrtho(), glViewport(), and operations on the GL_PROJECTION matrix.

  7. Drawing Triangles in 3D // Transform GL_MODELVIEW matrix // Repeat for every triangle glBegin(GL_TRIANGLES); for (i = 0; i < numTriangles; i++) { // Get vertices v1..v3 glVertex3f(v1.x, v1.y, v1.z); glVertex3f(v2.x, v2.y, v2.z); glVertex3f(v3.x, v3.y, v3.z); } glEnd(); BGLView::SwapBuffers();

  8. Putting Triangles and Textures Together

  9. Lighting the Model • Enable lighting with glEnable(). • Create lights with glLight(). • Eight lights can be created with parameters GL_LIGHT1...GL_LIGHT8. • Use glLightfv(GL_LIGHTi, GL_POSITION, &v) to place light. • Other parameters set the color, intensity, and shape of the light.

  10. Get More Code • OpenGL Programmers Guide and Reference Manual are available online (pester Vik for URLs). • Dr. Dobb’s journal has source code for Quake 2 model viewer at http://www.ddj.com/ftp/1998/1998_07/. • Be’s GLTeapot source code is in the /boot/optional directory. Model format is similar to the Quake format.

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