Function DrawColoredRing

Descent3/fireball.cpp:2073–2149

Draws a colored alpha ring...useful for cool lighting effects

// Draws a colored alpha ring...useful for cool lighting effects
void DrawColoredRing(vector *pos, float r, float g, float b, float inner_alpha, float outer_alpha, float size,
                     float inner_ring_ratio, uint8_t saturate, uint8_t lod) {
  static vector circleVecs[3][32];
  static int lodSegments[3] = {32, 16, 8};
  static bool firstCall = true;

  if (firstCall) {
    // initialize the circleVecs
    firstCall = false;
    int lodi;
    for (lodi = 0; lodi < 3; ++lodi) {
      int numSegments = lodSegments[lodi];
      int ringIncrement = 65536 / numSegments;
      int ringAngle = 0;
      int i;
      for (i = 0; i < numSegments; ++i, ringAngle += ringIncrement) {
        float ringSin = FixSin(ringAngle);
        float ringCos = FixCos(ringAngle);
        circleVecs[lodi][i].x = ringCos;
        circleVecs[lodi][i].y = ringSin;
        circleVecs[lodi][i].z = 0.0f;
      }
    }
  }

  // setup renderer
  rend_SetLighting(LS_GOURAUD);
  rend_SetTextureType(TT_FLAT);
  rend_SetOverlayType(OT_NONE);
  rend_SetColorModel(CM_RGB);
  rend_SetFlatColor(GR_RGB(r * 255, g * 255, b * 255));
  rend_SetAlphaType((saturate) ? AT_SATURATE_VERTEX : AT_VERTEX);

  // check LOD level
  ASSERT(lod >= 0 && lod <= 2);
  int i, numSegments = lodSegments[lod];

  // get the view matrix
  matrix viewOrient;
  g3_GetUnscaledMatrix(&viewOrient);
  viewOrient = ~viewOrient;

  // setup the points
  g3Point innerPoints[32], outerPoints[32];
  float innerRingSize = size * inner_ring_ratio;
  float outerRingSize = size;
  for (i = 0; i < numSegments; ++i) {
    vector worldSpaceCircleVec = circleVecs[lod][i] * viewOrient;
    vector innerPos = (*pos) + (worldSpaceCircleVec * innerRingSize);
    vector outerPos = (*pos) + (worldSpaceCircleVec * outerRingSize);

    g3_RotatePoint(&innerPoints[i], &innerPos);
    innerPoints[i].p3_flags |= PF_RGBA;
    innerPoints[i].p3_a = inner_alpha;
    innerPoints[i].p3_r = r;
    innerPoints[i].p3_g = g;
    innerPoints[i].p3_b = b;