Function RenderTerrain

Descent3/terrainrender.cpp:1308–1434

left,top,right,bot are optional parameters. Omiting them (or setting them to -1) will render to the whole screen. Passing valid values will only render tiles visible in the specified window (though it won't clip those tiles to the window)

// render to the whole screen.  Passing valid values will only render tiles visible in the
// specified window (though it won't clip those tiles to the window)
void RenderTerrain(uint8_t from_mine, int left, int top, int right, int bot) {
  static int first = 1;
  if (first) {
    InitTerrainRenderSpeedups();
    first = 0;
  }

  // Get the size of the current render window
  int render_width, render_height;
  rend_GetProjectionParameters(&render_width, &render_height);
  float w2 = ((float)render_width - 1) / 2.0f;
  float h2 = ((float)render_height - 1) / 2.0f;

  // Set up vars for (psuedo-)clipping window
  if (left < 0) {
    Check_terrain_portal = 0;
    left = 0;
  } else {
    int w = right - left;
    int h = bot - top;

    // If the portal takes up more than 50% the screen space then we don't check against it
    float threshold = (render_width * render_height) * 0.5f;
    if (w * h > threshold) {
      Check_terrain_portal = 0;
    } else {
      Check_terrain_portal = 1;
    }
  }

  if (top < 0) {
    top = 0;
  }
  if ((right == -1) || right > render_width)
    right = render_width - 1;
  if ((bot == -1) || bot > render_height)
    bot = render_height - 1;
  Clip_scale_left = left;
  Clip_scale_right = right;
  Clip_scale_top = top;
  Clip_scale_bot = bot;
  if (!Terrain_sky.textured) {
    rend_FillRect(Terrain_sky.sky_color, left, top, right + 1, bot + 1);
  }

  rend_SetFlatColor(Terrain_sky.sky_color);
  View_mode = GetFunctionMode();

  // Set this so we don't do reentrant rendering between terrain/mine
  Terrain_from_mine = from_mine;

#ifndef NEWEDITOR
  // See if we're supposed change the fog plane distance based on our framerate
  if (View_mode != EDITOR_MODE && ManageFramerate) {
    float fps = GetFPS();
    if (fps < MinAllowableFramerate) {
      if (Detail_settings.Terrain_render_distance > TERRAIN_SIZE) {
        Detail_settings.Terrain_render_distance -= (float)(TERRAIN_SIZE / 4);