tr_sky.c

quakeIII源码这个不用我多说吧

			sky_mins_subd[1] = HALF_SKY_SUBDIVISIONS;

		if ( sky_maxs_subd[0] < -HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[0] = -HALF_SKY_SUBDIVISIONS;
		else if ( sky_maxs_subd[0] > HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[0] = HALF_SKY_SUBDIVISIONS;
		if ( sky_maxs_subd[1] < -HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[1] = -HALF_SKY_SUBDIVISIONS;
		else if ( sky_maxs_subd[1] > HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[1] = HALF_SKY_SUBDIVISIONS;

		//
		// iterate through the subdivisions
		//
		for ( t = sky_mins_subd[1]+HALF_SKY_SUBDIVISIONS; t <= sky_maxs_subd[1]+HALF_SKY_SUBDIVISIONS; t++ )
		{
			for ( s = sky_mins_subd[0]+HALF_SKY_SUBDIVISIONS; s <= sky_maxs_subd[0]+HALF_SKY_SUBDIVISIONS; s++ )
			{
				MakeSkyVec( ( s - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							( t - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							i, 
							s_skyTexCoords[t][s], 
							s_skyPoints[t][s] );
			}
		}

		DrawSkySide( shader->sky.outerbox[sky_texorder[i]],
			         sky_mins_subd,
					 sky_maxs_subd );
	}

}

static void FillCloudySkySide( const int mins[2], const int maxs[2], qboolean addIndexes )
{
	int s, t;
	int vertexStart = tess.numVertexes;
	int tHeight, sWidth;

	tHeight = maxs[1] - mins[1] + 1;
	sWidth = maxs[0] - mins[0] + 1;

	for ( t = mins[1]+HALF_SKY_SUBDIVISIONS; t <= maxs[1]+HALF_SKY_SUBDIVISIONS; t++ )
	{
		for ( s = mins[0]+HALF_SKY_SUBDIVISIONS; s <= maxs[0]+HALF_SKY_SUBDIVISIONS; s++ )
		{
			VectorAdd( s_skyPoints[t][s], backEnd.viewParms.or.origin, tess.xyz[tess.numVertexes] );
			tess.texCoords[tess.numVertexes][0][0] = s_skyTexCoords[t][s][0];
			tess.texCoords[tess.numVertexes][0][1] = s_skyTexCoords[t][s][1];

			tess.numVertexes++;

			if ( tess.numVertexes >= SHADER_MAX_VERTEXES )
			{
				ri.Error( ERR_DROP, "SHADER_MAX_VERTEXES hit in FillCloudySkySide()\n" );
			}
		}
	}

	// only add indexes for one pass, otherwise it would draw multiple times for each pass
	if ( addIndexes ) {
		for ( t = 0; t < tHeight-1; t++ )
		{	
			for ( s = 0; s < sWidth-1; s++ )
			{
				tess.indexes[tess.numIndexes] = vertexStart + s + t * ( sWidth );
				tess.numIndexes++;
				tess.indexes[tess.numIndexes] = vertexStart + s + ( t + 1 ) * ( sWidth );
				tess.numIndexes++;
				tess.indexes[tess.numIndexes] = vertexStart + s + 1 + t * ( sWidth );
				tess.numIndexes++;

				tess.indexes[tess.numIndexes] = vertexStart + s + ( t + 1 ) * ( sWidth );
				tess.numIndexes++;
				tess.indexes[tess.numIndexes] = vertexStart + s + 1 + ( t + 1 ) * ( sWidth );
				tess.numIndexes++;
				tess.indexes[tess.numIndexes] = vertexStart + s + 1 + t * ( sWidth );
				tess.numIndexes++;
			}
		}
	}
}

static void FillCloudBox( const shader_t *shader, int stage )
{
	int i;

	for ( i =0; i < 6; i++ )
	{
		int sky_mins_subd[2], sky_maxs_subd[2];
		int s, t;
		float MIN_T;

		if ( 1 ) // FIXME? shader->sky.fullClouds )
		{
			MIN_T = -HALF_SKY_SUBDIVISIONS;

			// still don't want to draw the bottom, even if fullClouds
			if ( i == 5 )
				continue;
		}
		else
		{
			switch( i )
			{
			case 0:
			case 1:
			case 2:
			case 3:
				MIN_T = -1;
				break;
			case 5:
				// don't draw clouds beneath you
				continue;
			case 4:		// top
			default:
				MIN_T = -HALF_SKY_SUBDIVISIONS;
				break;
			}
		}

		sky_mins[0][i] = floor( sky_mins[0][i] * HALF_SKY_SUBDIVISIONS ) / HALF_SKY_SUBDIVISIONS;
		sky_mins[1][i] = floor( sky_mins[1][i] * HALF_SKY_SUBDIVISIONS ) / HALF_SKY_SUBDIVISIONS;
		sky_maxs[0][i] = ceil( sky_maxs[0][i] * HALF_SKY_SUBDIVISIONS ) / HALF_SKY_SUBDIVISIONS;
		sky_maxs[1][i] = ceil( sky_maxs[1][i] * HALF_SKY_SUBDIVISIONS ) / HALF_SKY_SUBDIVISIONS;

		if ( ( sky_mins[0][i] >= sky_maxs[0][i] ) ||
			 ( sky_mins[1][i] >= sky_maxs[1][i] ) )
		{
			continue;
		}

		sky_mins_subd[0] = myftol( sky_mins[0][i] * HALF_SKY_SUBDIVISIONS );
		sky_mins_subd[1] = myftol( sky_mins[1][i] * HALF_SKY_SUBDIVISIONS );
		sky_maxs_subd[0] = myftol( sky_maxs[0][i] * HALF_SKY_SUBDIVISIONS );
		sky_maxs_subd[1] = myftol( sky_maxs[1][i] * HALF_SKY_SUBDIVISIONS );

		if ( sky_mins_subd[0] < -HALF_SKY_SUBDIVISIONS ) 
			sky_mins_subd[0] = -HALF_SKY_SUBDIVISIONS;
		else if ( sky_mins_subd[0] > HALF_SKY_SUBDIVISIONS ) 
			sky_mins_subd[0] = HALF_SKY_SUBDIVISIONS;
		if ( sky_mins_subd[1] < MIN_T )
			sky_mins_subd[1] = MIN_T;
		else if ( sky_mins_subd[1] > HALF_SKY_SUBDIVISIONS ) 
			sky_mins_subd[1] = HALF_SKY_SUBDIVISIONS;

		if ( sky_maxs_subd[0] < -HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[0] = -HALF_SKY_SUBDIVISIONS;
		else if ( sky_maxs_subd[0] > HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[0] = HALF_SKY_SUBDIVISIONS;
		if ( sky_maxs_subd[1] < MIN_T )
			sky_maxs_subd[1] = MIN_T;
		else if ( sky_maxs_subd[1] > HALF_SKY_SUBDIVISIONS ) 
			sky_maxs_subd[1] = HALF_SKY_SUBDIVISIONS;

		//
		// iterate through the subdivisions
		//
		for ( t = sky_mins_subd[1]+HALF_SKY_SUBDIVISIONS; t <= sky_maxs_subd[1]+HALF_SKY_SUBDIVISIONS; t++ )
		{
			for ( s = sky_mins_subd[0]+HALF_SKY_SUBDIVISIONS; s <= sky_maxs_subd[0]+HALF_SKY_SUBDIVISIONS; s++ )
			{
				MakeSkyVec( ( s - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							( t - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							i, 
							NULL,
							s_skyPoints[t][s] );

				s_skyTexCoords[t][s][0] = s_cloudTexCoords[i][t][s][0];
				s_skyTexCoords[t][s][1] = s_cloudTexCoords[i][t][s][1];
			}
		}

		// only add indexes for first stage
		FillCloudySkySide( sky_mins_subd, sky_maxs_subd, ( stage == 0 ) );
	}
}

/*
** R_BuildCloudData
*/
void R_BuildCloudData( shaderCommands_t *input )
{
	int			i;
	shader_t	*shader;

	shader = input->shader;

	assert( shader->isSky );

	sky_min = 1.0 / 256.0f;		// FIXME: not correct?
	sky_max = 255.0 / 256.0f;

	// set up for drawing
	tess.numIndexes = 0;
	tess.numVertexes = 0;

	if ( input->shader->sky.cloudHeight )
	{
		for ( i = 0; i < MAX_SHADER_STAGES; i++ )
		{
			if ( !tess.xstages[i] ) {
				break;
			}
			FillCloudBox( input->shader, i );
		}
	}
}

/*
** R_InitSkyTexCoords
** Called when a sky shader is parsed
*/
#define SQR( a ) ((a)*(a))
void R_InitSkyTexCoords( float heightCloud )
{
	int i, s, t;
	float radiusWorld = 4096;
	float p;
	float sRad, tRad;
	vec3_t skyVec;
	vec3_t v;

	// init zfar so MakeSkyVec works even though
	// a world hasn't been bounded
	backEnd.viewParms.zFar = 1024;

	for ( i = 0; i < 6; i++ )
	{
		for ( t = 0; t <= SKY_SUBDIVISIONS; t++ )
		{
			for ( s = 0; s <= SKY_SUBDIVISIONS; s++ )
			{
				// compute vector from view origin to sky side integral point
				MakeSkyVec( ( s - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							( t - HALF_SKY_SUBDIVISIONS ) / ( float ) HALF_SKY_SUBDIVISIONS, 
							i, 
							NULL,
							skyVec );

				// compute parametric value 'p' that intersects with cloud layer
				p = ( 1.0f / ( 2 * DotProduct( skyVec, skyVec ) ) ) *
					( -2 * skyVec[2] * radiusWorld + 
					   2 * sqrt( SQR( skyVec[2] ) * SQR( radiusWorld ) + 
					             2 * SQR( skyVec[0] ) * radiusWorld * heightCloud +
								 SQR( skyVec[0] ) * SQR( heightCloud ) + 
								 2 * SQR( skyVec[1] ) * radiusWorld * heightCloud +
								 SQR( skyVec[1] ) * SQR( heightCloud ) + 
								 2 * SQR( skyVec[2] ) * radiusWorld * heightCloud +
								 SQR( skyVec[2] ) * SQR( heightCloud ) ) );

				s_cloudTexP[i][t][s] = p;

				// compute intersection point based on p
				VectorScale( skyVec, p, v );
				v[2] += radiusWorld;

				// compute vector from world origin to intersection point 'v'
				VectorNormalize( v );

				sRad = Q_acos( v[0] );
				tRad = Q_acos( v[1] );

				s_cloudTexCoords[i][t][s][0] = sRad;
				s_cloudTexCoords[i][t][s][1] = tRad;
			}
		}
	}
}

//======================================================================================

/*
** RB_DrawSun
*/
void RB_DrawSun( void ) {
	float		size;
	float		dist;
	vec3_t		origin, vec1, vec2;
	vec3_t		temp;

	if ( !backEnd.skyRenderedThisView ) {
		return;
	}
	if ( !r_drawSun->integer ) {
		return;
	}
	qglLoadMatrixf( backEnd.viewParms.world.modelMatrix );
	qglTranslatef (backEnd.viewParms.or.origin[0], backEnd.viewParms.or.origin[1], backEnd.viewParms.or.origin[2]);

	dist = 	backEnd.viewParms.zFar / 1.75;		// div sqrt(3)
	size = dist * 0.4;

	VectorScale( tr.sunDirection, dist, origin );
	PerpendicularVector( vec1, tr.sunDirection );
	CrossProduct( tr.sunDirection, vec1, vec2 );

	VectorScale( vec1, size, vec1 );
	VectorScale( vec2, size, vec2 );

	// farthest depth range
	qglDepthRange( 1.0, 1.0 );

	// FIXME: use quad stamp
	RB_BeginSurface( tr.sunShader, tess.fogNum );
		VectorCopy( origin, temp );
		VectorSubtract( temp, vec1, temp );
		VectorSubtract( temp, vec2, temp );
		VectorCopy( temp, tess.xyz[tess.numVertexes] );
		tess.texCoords[tess.numVertexes][0][0] = 0;
		tess.texCoords[tess.numVertexes][0][1] = 0;
		tess.vertexColors[tess.numVertexes][0] = 255;
		tess.vertexColors[tess.numVertexes][1] = 255;
		tess.vertexColors[tess.numVertexes][2] = 255;
		tess.numVertexes++;

		VectorCopy( origin, temp );
		VectorAdd( temp, vec1, temp );
		VectorSubtract( temp, vec2, temp );
		VectorCopy( temp, tess.xyz[tess.numVertexes] );
		tess.texCoords[tess.numVertexes][0][0] = 0;
		tess.texCoords[tess.numVertexes][0][1] = 1;
		tess.vertexColors[tess.numVertexes][0] = 255;
		tess.vertexColors[tess.numVertexes][1] = 255;
		tess.vertexColors[tess.numVertexes][2] = 255;
		tess.numVertexes++;

		VectorCopy( origin, temp );
		VectorAdd( temp, vec1, temp );
		VectorAdd( temp, vec2, temp );
		VectorCopy( temp, tess.xyz[tess.numVertexes] );
		tess.texCoords[tess.numVertexes][0][0] = 1;
		tess.texCoords[tess.numVertexes][0][1] = 1;
		tess.vertexColors[tess.numVertexes][0] = 255;
		tess.vertexColors[tess.numVertexes][1] = 255;
		tess.vertexColors[tess.numVertexes][2] = 255;
		tess.numVertexes++;

		VectorCopy( origin, temp );
		VectorSubtract( temp, vec1, temp );
		VectorAdd( temp, vec2, temp );
		VectorCopy( temp, tess.xyz[tess.numVertexes] );
		tess.texCoords[tess.numVertexes][0][0] = 1;
		tess.texCoords[tess.numVertexes][0][1] = 0;
		tess.vertexColors[tess.numVertexes][0] = 255;
		tess.vertexColors[tess.numVertexes][1] = 255;
		tess.vertexColors[tess.numVertexes][2] = 255;
		tess.numVertexes++;

		tess.indexes[tess.numIndexes++] = 0;
		tess.indexes[tess.numIndexes++] = 1;
		tess.indexes[tess.numIndexes++] = 2;
		tess.indexes[tess.numIndexes++] = 0;
		tess.indexes[tess.numIndexes++] = 2;
		tess.indexes[tess.numIndexes++] = 3;

	RB_EndSurface();

	// back to normal depth range
	qglDepthRange( 0.0, 1.0 );
}




/*
================
RB_StageIteratorSky

All of the visible sky triangles are in tess

Other things could be stuck in here, like birds in the sky, etc
================
*/
void RB_StageIteratorSky( void ) {
	if ( r_fastsky->integer ) {
		return;
	}

	// go through all the polygons and project them onto
	// the sky box to see which blocks on each side need
	// to be drawn
	RB_ClipSkyPolygons( &tess );

	// r_showsky will let all the sky blocks be drawn in
	// front of everything to allow developers to see how
	// much sky is getting sucked in
	if ( r_showsky->integer ) {
		qglDepthRange( 0.0, 0.0 );
	} else {
		qglDepthRange( 1.0, 1.0 );
	}

	// draw the outer skybox
	if ( tess.shader->sky.outerbox[0] && tess.shader->sky.outerbox[0] != tr.defaultImage ) {
		qglColor3f( tr.identityLight, tr.identityLight, tr.identityLight );
		
		qglPushMatrix ();
		GL_State( 0 );
		qglTranslatef (backEnd.viewParms.or.origin[0], backEnd.viewParms.or.origin[1], backEnd.viewParms.or.origin[2]);

		DrawSkyBox( tess.shader );

		qglPopMatrix();
	}

	// generate the vertexes for all the clouds, which will be drawn
	// by the generic shader routine
	R_BuildCloudData( &tess );

	RB_StageIteratorGeneric();

	// draw the inner skybox


	// back to normal depth range
	qglDepthRange( 0.0, 1.0 );

	// note that sky was drawn so we will draw a sun later
	backEnd.skyRenderedThisView = qtrue;
}