Table of Contents Glide Programming Guide

9Error Handling

The callback function accepts a string describing the error and a flag indicating if the error is fatal or recoverable. grErrorSetCallback() is relevant only when using the debugging version of Glide; the release build of Glide removes all internal parameter validation and error checking so the callback function will never be called.

Chapter 4. Rendering Primitives

1In This Chapter

You will learn how to:

• 
  establish a clipping window
  
• 
  draw a point, a line, a triangle, or a convex polygon on the screen
  
• 
  cull back-facing polygons from the scene
  
• 
  draw an anti-aliased point, line, triangle, or convex polygon
  

2The GrVertex Structure

The GrVertex structure, first presented in Chapter 2, collects together all the parameters that define a vertex. In this chapter, only the x and y coordinates will be discussed; the other parameters are called into play in later chapters.
typedef struct {
float x, y, z; /* x, y, z of screen space. Z is ignored */
float ooz; /* 65535/z (used for z buffering) */
float oow; /* 1/w (used for w buffering) */
float r, g, b, a; /* red, green, blue, and alpha ([0..255.0]) */
GrTmuVertex tmuvtx[GLIDE_NUM_TMU];
} GrVertex;
The x and y coordinates are 32-bit floating point values that represent the position of the vertex in screen space. While the Voodoo Graphics hardware renders only triangles, Glide provides functions to draw points, lines, and polygons as well as triangles.
When a point, line, triangle, or polygon is rendered, its appearance will reflect the current state of the rendering pipeline. That is, if texture mapping is enabled, then the point, line, triangle, or polygon will be texture mapped. Similarly, alpha blending, fogging, color, and lighting effects, chroma-keying, and other special effects will contribute to the appearance of any and all geometric shapes drawn while they are enabled.

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