自学教程：C++ ClipSkyPolygon函数代码示例

/*=================R_DrawSkyChain=================*/void R_DrawSkyChain (msurface_t *s){    msurface_t  *fa;    int     i;    vec3_t  verts[MAX_CLIP_VERTS];    glpoly_t    *p;    c_sky = 0;    GL_Bind(solidskytexture);    // calculate vertex values for sky box    for (fa=s ; fa ; fa=fa->texturechain)    {        for (p=fa->polys ; p ; p=p->next)        {            for (i=0 ; i<p->numverts ; i++)            {                VectorSubtract (p->verts[i], r_origin, verts[i]);            }            ClipSkyPolygon (p->numverts, verts[0], 0);        }    }}

/*=================R_AddSkySurface=================*/void R_AddSkySurface (const msurface_t *fa){	int			i;	vec3_t		verts[MAX_CLIP_VERTS];	const glpoly_t	*p;	// calculate vertex values for sky box	for (i = 0, p = fa->polys; i < p->numverts; i++)		VectorSubtract (p->verts[i], r_origin, verts[i]);	ClipSkyPolygon (p->numverts, verts[0], 0);}

static void RB_ClipSkyPolygons( const shaderCommands_t* input ){	vec3_t p[4];	// need one extra point for clipping	ClearSkyBox();	for ( int i = 0; i < input->numIndexes; i += 3 ) {		VectorSubtract( input->xyz[input->indexes[i+0]], backEnd.viewParms.or.origin, p[0] );		VectorSubtract( input->xyz[input->indexes[i+1]], backEnd.viewParms.or.origin, p[1] );		VectorSubtract( input->xyz[input->indexes[i+2]], backEnd.viewParms.or.origin, p[2] );		ClipSkyPolygon( 3, p[0], 0 );	}}

/* * RB_ClipSkyPolygons */voidRB_ClipSkyPolygons(shaderCommands_t *input){	Vec3	p[5];	/* need one extra point for clipping */	int	i, j;	ClearSkyBox();	for(i = 0; i < input->numIndexes; i += 3){		for(j = 0; j < 3; j++)			subv3(input->xyz[input->indexes[i+j]],				backEnd.viewParms.or.origin,				p[j]);		ClipSkyPolygon(3, p[0], 0);	}}

/*================Tess_ClipSkyPolygons================*/void Tess_ClipSkyPolygons(){	vec3_t p[ 5 ]; // need one extra point for clipping	unsigned int i, j;	ClearSkyBox();	for ( i = 0; i < tess.numIndexes; i += 3 )	{		for ( j = 0; j < 3; j++ )		{			VectorSubtract( tess.xyz[ tess.indexes[ i + j ] ], backEnd.viewParms.orientation.origin, p[ j ] );		}		ClipSkyPolygon( 3, p[ 0 ], 0 );	}}

void RB_ClipSkyPolygons( shaderCommands_t *input ) {    vector3		p[5];	// need one extra point for clipping    int			i, j;    ClearSkyBox();    for ( i = 0; i < input->numIndexes; i += 3 )    {        for (j = 0 ; j < 3 ; j++)        {            VectorSubtract( &input->xyz[input->indexes[i+j]],                            &backEnd.viewParms.or.origin,                            &p[j] );        }        ClipSkyPolygon( 3, &p[0], 0 );    }}

/*	R_DrawSkyChain*/voidR_DrawSkyChain ( msurface_t *s ){	msurface_t	*fa;	int		i;	vec3_t	verts[MAX_CLIP_VERTS];	glpoly_t	*p;	if (r_sky->value) {		c_sky = 0;		GL_Bind(solidskytexture);		// calculate vertex values for sky box		for (fa=s ; fa ; fa=fa->texturechain) {			for (p=fa->polys ; p ; p=p->next) {				for (i=0 ; i<p->numverts ; i++) {					VectorSubtract (p->verts[i], r_origin, verts[i]);				}				ClipSkyPolygon (p->numverts, verts[0], 0);			}		}	} else {		GL_DisableMultitexture();		// used when gl_texsort is on		GL_Bind(solidskytexture);		speedscale = realtime*8;		speedscale -= (int)speedscale & ~127 ;		for (fa=s ; fa ; fa=fa->texturechain)			EmitSkyPolys (fa);		glEnable (GL_BLEND);		GL_Bind (alphaskytexture);		speedscale = realtime*16;		speedscale -= (int)speedscale & ~127 ;		for ( fa=s ; fa != NULL ; fa = fa->texturechain )			EmitSkyPolys (fa);		glDisable (GL_BLEND);	}}

/*=================R_AddSkySurface=================*/void R_AddSkySurface( mface_t *fa ) {    int         i;    vec3_t      verts[MAX_CLIP_VERTS];    msurfedge_t *surfedge;    mvertex_t   *vert;    medge_t     *edge;    if( fa->numsurfedges > MAX_CLIP_VERTS ) {        Com_Error( ERR_DROP, "%s: too many verts", __func__ );    }    // calculate vertex values for sky box    surfedge = fa->firstsurfedge;    for( i = 0; i < fa->numsurfedges; i++, surfedge++ ) {        edge = surfedge->edge;        vert = edge->v[surfedge->vert];        VectorSubtract (vert->point, glr.fd.vieworg, verts[i]);    }    ClipSkyPolygon (fa->numsurfedges, verts[0], 0);}

/** R_ClipSkySurface*/bool R_ClipSkySurface( drawSurfaceSky_t *drawSurf, const msurface_t *surf ) {	int i;	const vec4_t *vert;	const elem_t *elem;	const mesh_t *mesh;	vec3_t verts[4];	int axis = -1;	// calculate vertex values for sky box	mesh = &surf->mesh;	elem = mesh->elems;	vert = mesh->xyzArray;	for( i = 0; i < mesh->numElems; i += 3, elem += 3 ) {		VectorSubtract( vert[elem[0]], rn.viewOrigin, verts[0] );		VectorSubtract( vert[elem[1]], rn.viewOrigin, verts[1] );		VectorSubtract( vert[elem[2]], rn.viewOrigin, verts[2] );		ClipSkyPolygon( drawSurf, 3, verts[0], 0, &axis );	}	return axis != -1;}

/*================ClipSkyPolygon================*/static void ClipSkyPolygon (int nump, bvec3_t vecs, int stage) {	bfixed	*norm;	bfixed	*v;	qboolean	front, back;	bfixed	d, e;	bfixed	dists[MAX_CLIP_VERTS];	int		sides[MAX_CLIP_VERTS];	bvec3_t	newv[2][MAX_CLIP_VERTS];	int		newc[2];	int		i, j;	if (nump > MAX_CLIP_VERTS-2)		ri.Error (ERR_DROP, "ClipSkyPolygon: MAX_CLIP_VERTS");	if (stage == 6)	{	// fully clipped, so draw it		AddSkyPolygon (nump, vecs);		return;	}	front = back = qfalse;	norm = sky_clip[stage];	for (i=0, v = vecs ; i<nump ; i++, v+=3)	{		d = FIXED_VEC3DOT (v, norm);		if (d > ON_EPSILON)		{			front = qtrue;			sides[i] = SIDE_FRONT;		}		else if (d < -ON_EPSILON)		{			back = qtrue;			sides[i] = SIDE_BACK;		}		else			sides[i] = SIDE_ON;		dists[i] = d;	}	if (!front || !back)	{	// not clipped		ClipSkyPolygon (nump, vecs, stage+1);		return;	}	// clip it	sides[i] = sides[0];	dists[i] = dists[0];	VectorCopy (vecs, (vecs+(i*3)) );	newc[0] = newc[1] = 0;	for (i=0, v = vecs ; i<nump ; i++, v+=3)	{		switch (sides[i])		{		case SIDE_FRONT:			VectorCopy (v, newv[0][newc[0]]);			newc[0]++;			break;		case SIDE_BACK:			VectorCopy (v, newv[1][newc[1]]);			newc[1]++;			break;		case SIDE_ON:			VectorCopy (v, newv[0][newc[0]]);			newc[0]++;			VectorCopy (v, newv[1][newc[1]]);			newc[1]++;			break;		}		if (sides[i] == SIDE_ON || sides[i+1] == SIDE_ON || sides[i+1] == sides[i])			continue;		d = dists[i] / (dists[i] - dists[i+1]);		for (j=0 ; j<3 ; j++)		{			e = v[j] + d*(v[j+3] - v[j]);			newv[0][newc[0]][j] = e;			newv[1][newc[1]][j] = e;		}		newc[0]++;		newc[1]++;	}	// continue	ClipSkyPolygon (newc[0], newv[0][0], stage+1);	ClipSkyPolygon (newc[1], newv[1][0], stage+1);}

static void ClipSkyPolygon (int nump, vec3_t vecs, int stage){	float	*norm;	float	*v;	qboolean	front, back;	float	d, e;	float	dists[MAX_CLIP_VERTS];	int		sides[MAX_CLIP_VERTS];	vec3_t	newv[2][MAX_CLIP_VERTS];	int		newc[2];	int		i, j;	if (nump > MAX_CLIP_VERTS-2)		Sys_Error ("%s: MAX_CLIP_VERTS", __thisfunc__);	if (stage == 6)	{	// fully clipped, so draw it		DrawSkyPolygon (nump, vecs);		return;	}	front = back = false;	norm = skyclip[stage];	for (i = 0, v = vecs; i < nump; i++, v += 3)	{		d = DotProduct (v, norm);		if (d > ON_EPSILON)		{			front = true;			sides[i] = SIDE_FRONT;		}		else if (d < ON_EPSILON)		{			back = true;			sides[i] = SIDE_BACK;		}		else			sides[i] = SIDE_ON;		dists[i] = d;	}	if (!front || !back)	{	// not clipped		ClipSkyPolygon (nump, vecs, stage+1);		return;	}	// clip it	sides[i] = sides[0];	dists[i] = dists[0];	VectorCopy (vecs, (vecs+(i*3)) );	newc[0] = newc[1] = 0;	for (i = 0, v = vecs; i < nump; i++, v += 3)	{		switch (sides[i])		{		case SIDE_FRONT:			VectorCopy (v, newv[0][newc[0]]);			newc[0]++;			break;		case SIDE_BACK:			VectorCopy (v, newv[1][newc[1]]);			newc[1]++;			break;		case SIDE_ON:			VectorCopy (v, newv[0][newc[0]]);			newc[0]++;			VectorCopy (v, newv[1][newc[1]]);			newc[1]++;			break;		}		if (sides[i] == SIDE_ON || sides[i+1] == SIDE_ON || sides[i+1] == sides[i])			continue;		d = dists[i] / (dists[i] - dists[i+1]);		for (j = 0; j < 3; j++)		{			e = v[j] + d*(v[j+3] - v[j]);			newv[0][newc[0]][j] = e;			newv[1][newc[1]][j] = e;		}		newc[0]++;		newc[1]++;	}	// continue	ClipSkyPolygon (newc[0], newv[0][0], stage+1);	ClipSkyPolygon (newc[1], newv[1][0], stage+1);}

void Sky_Render(DrawCallList *drawCallList, vec3 cameraPosition, float zMax, const SkySurface &surface){	assert(drawCallList);	const bool shouldDrawSkyBox = surface.material->sky.outerbox[0] && surface.material->sky.outerbox[0] != Texture::getDefault();	const bool shouldDrawCloudBox = surface.material->sky.cloudHeight > 0 && surface.material->stages[0].active;	if (!shouldDrawSkyBox && !shouldDrawCloudBox)		return;	// Clear sky box.	for (size_t i = 0; i < 6; i++)	{		sky_mins[0][i] = sky_mins[1][i] = 9999;		sky_maxs[0][i] = sky_maxs[1][i] = -9999;	}	// Clip sky polygons.	for (size_t i = 0; i < surface.vertices.size(); i += 3)	{		vec3 p[5]; // need one extra point for clipping		for (size_t j = 0 ; j < 3 ; j++) 		{			p[j] = surface.vertices[i + j].pos - cameraPosition;		}		ClipSkyPolygon(3, p, 0);	}	// Draw the skybox.	if (shouldDrawSkyBox)	{		for (int i = 0; i < 6; i++)		{			uint32_t nVertices, nIndices;			sky_min = 0;			sky_max = 1;			memset( s_skyTexCoords, 0, sizeof( s_skyTexCoords ) );			if (!TessellateSkyBoxSide(i, nullptr, nullptr, &nVertices, &nIndices, cameraPosition, zMax))				continue;			DrawCall dc;			if (!bgfx::allocTransientBuffers(&dc.vb.transientHandle, Vertex::decl, nVertices, &dc.ib.transientHandle, nIndices)) 			{				WarnOnce(WarnOnceId::TransientBuffer);				return;			}			sky_min = 0;			sky_max = 1;			memset( s_skyTexCoords, 0, sizeof( s_skyTexCoords ) );			TessellateSkyBoxSide(i, (Vertex *)dc.vb.transientHandle.data, (uint16_t *)dc.ib.transientHandle.data, nullptr, nullptr, cameraPosition, zMax);			dc.vb.type = dc.ib.type = DrawCall::BufferType::Transient;			dc.vb.nVertices = nVertices;			dc.ib.nIndices = nIndices;			dc.flags = DrawCallFlags::Sky | DrawCallFlags::Skybox;			dc.material = surface.material;			dc.skyboxSide = i;			dc.state |= BGFX_STATE_DEPTH_TEST_LEQUAL;			// Write depth as 1.			dc.zOffset = 1.0f;			dc.zScale = 0.0f;			drawCallList->push_back(dc);		}	}	// Draw the clouds.	if (shouldDrawCloudBox)	{		uint32_t nVertices, nIndices;		TessellateCloudBox(nullptr, nullptr, &nVertices, &nIndices, cameraPosition, zMax);		DrawCall dc;		if (!bgfx::allocTransientBuffers(&dc.vb.transientHandle, Vertex::decl, nVertices, &dc.ib.transientHandle, nIndices)) 		{			WarnOnce(WarnOnceId::TransientBuffer);			return;		}		TessellateCloudBox((Vertex *)dc.vb.transientHandle.data, (uint16_t *)dc.ib.transientHandle.data, nullptr, nullptr, cameraPosition, zMax);		dc.vb.type = dc.ib.type = DrawCall::BufferType::Transient;		dc.vb.nVertices = nVertices;		dc.ib.nIndices = nIndices;		dc.flags = DrawCallFlags::Sky;		dc.material = surface.material;		dc.sort = 1; // Render after the skybox.		// Write depth as 1.		dc.zOffset = 1.0f;		dc.zScale = 0.0f;		drawCallList->push_back(dc);	}}

static void ClipSkyPolygon(int nump, vec3 *vecs, int stage) {	bool front, back;	float	d, e;	float	dists[MAX_CLIP_VERTS];	int		sides[MAX_CLIP_VERTS];	vec3	newv[2][MAX_CLIP_VERTS];	int		newc[2];	int		i, j;	if (nump > MAX_CLIP_VERTS-2)		interface::Error("ClipSkyPolygon: MAX_CLIP_VERTS");	if (stage == 6)	{	// fully clipped, so draw it		AddSkyPolygon (nump, vecs);		return;	}	front = back = false;	for (i=0; i<nump ; i++)	{		d = vec3::dotProduct(vecs[i], sky_clip[stage]);		if (d > ON_EPSILON)		{			front = true;			sides[i] = SIDE_FRONT;		}		else if (d < -ON_EPSILON)		{			back = true;			sides[i] = SIDE_BACK;		}		else			sides[i] = SIDE_ON;		dists[i] = d;	}	if (!front || !back)	{	// not clipped		ClipSkyPolygon (nump, vecs, stage+1);		return;	}	// clip it	sides[i] = sides[0];	dists[i] = dists[0];	vecs[i] = vecs[0];	newc[0] = newc[1] = 0;	for (i=0; i<nump ; i++)	{		const vec3 &v = vecs[i];		switch (sides[i])		{		case SIDE_FRONT:			newv[0][newc[0]] = v;			newc[0]++;			break;		case SIDE_BACK:			newv[1][newc[1]] = v;			newc[1]++;			break;		case SIDE_ON:			newv[0][newc[0]] = v;			newc[0]++;			newv[1][newc[1]] = v;			newc[1]++;			break;		}		if (sides[i] == SIDE_ON || sides[i+1] == SIDE_ON || sides[i+1] == sides[i])			continue;		d = dists[i] / (dists[i] - dists[i+1]);		for (j=0 ; j<3 ; j++)		{			e = v[j] + d*(vecs[i + 1][j] - v[j]);			newv[0][newc[0]][j] = e;			newv[1][newc[1]][j] = e;		}		newc[0]++;		newc[1]++;	}	// continue	ClipSkyPolygon(newc[0], &newv[0][0], stage+1);	ClipSkyPolygon(newc[1], &newv[1][0], stage+1);}

/** ClipSkyPolygon*/static void ClipSkyPolygon( drawSurfaceSky_t *drawSurf, int nump, vec_t *vecs, int stage, int *visAxis ) {	const float *norm;	float *v;	bool front, back;	float d, e;	float dists[MAX_CLIP_VERTS + 1];	int sides[MAX_CLIP_VERTS + 1];	vec3_t newv[2][MAX_CLIP_VERTS + 1];	int newc[2];	int i, j;	if( nump > MAX_CLIP_VERTS ) {		ri.Com_Error( ERR_DROP, "ClipSkyPolygon: MAX_CLIP_VERTS" );		return;	}loc1:	if( stage == 6 ) {		// fully clipped, so draw it		DrawSkyPolygon( drawSurf, nump, vecs, visAxis );		return;	}	front = back = false;	norm = skyclip[stage];	for( i = 0, v = vecs; i < nump; i++, v += 3 ) {		d = DotProduct( v, norm );		if( d > ON_EPSILON ) {			front = true;			sides[i] = SIDE_FRONT;		} else if( d < -ON_EPSILON ) {			back = true;			sides[i] = SIDE_BACK;		} else {			sides[i] = SIDE_ON;		}		dists[i] = d;	}	if( !front || !back ) { // not clipped		stage++;		goto loc1;	}	// clip it	sides[i] = sides[0];	dists[i] = dists[0];	VectorCopy( vecs, ( vecs + ( i * 3 ) ) );	newc[0] = newc[1] = 0;	for( i = 0, v = vecs; i < nump; i++, v += 3 ) {		switch( sides[i] ) {			case SIDE_FRONT:				VectorCopy( v, newv[0][newc[0]] );				newc[0]++;				break;			case SIDE_BACK:				VectorCopy( v, newv[1][newc[1]] );				newc[1]++;				break;			case SIDE_ON:				VectorCopy( v, newv[0][newc[0]] );				newc[0]++;				VectorCopy( v, newv[1][newc[1]] );				newc[1]++;				break;		}		if( sides[i] == SIDE_ON || sides[i + 1] == SIDE_ON || sides[i + 1] == sides[i] ) {			continue;		}		d = dists[i] / ( dists[i] - dists[i + 1] );		for( j = 0; j < 3; j++ ) {			e = v[j] + d * ( v[j + 3] - v[j] );			newv[0][newc[0]][j] = e;			newv[1][newc[1]][j] = e;		}		newc[0]++;		newc[1]++;	}	// continue	ClipSkyPolygon( drawSurf, newc[0], newv[0][0], stage + 1, visAxis );	ClipSkyPolygon( drawSurf, newc[1], newv[1][0], stage + 1, visAxis );}

/* * ClipSkyPolygon */static voidClipSkyPolygon(int nump, Vec3 vecs, int stage){	float *norm;	float *v;	qbool		front, back;	float		d, e;	float		dists[MAX_CLIP_VERTS];	int		sides[MAX_CLIP_VERTS];	Vec3		newv[2][MAX_CLIP_VERTS];	int		newc[2];	int		i, j;	if(nump > MAX_CLIP_VERTS-2)		ri.Error (ERR_DROP, "ClipSkyPolygon: MAX_CLIP_VERTS");	if(stage == 6){	/* fully clipped, so draw it */		AddSkyPolygon (nump, vecs);		return;	}	front	= back = qfalse;	norm	= sky_clip[stage];	for(i=0, v = vecs; i<nump; i++, v+=3){		d = dotv3 (v, norm);		if(d > ON_EPSILON){			front = qtrue;			sides[i] = SIDE_FRONT;		}else if(d < -ON_EPSILON){			back = qtrue;			sides[i] = SIDE_BACK;		}else			sides[i] = SIDE_ON;		dists[i] = d;	}	if(!front || !back){	/* not clipped */		ClipSkyPolygon (nump, vecs, stage+1);		return;	}	/* clip it */	sides[i] = sides[0];	dists[i] = dists[0];	copyv3 (vecs, (vecs+(i*3)));	newc[0] = newc[1] = 0;	for(i=0, v = vecs; i<nump; i++, v+=3){		switch(sides[i]){		case SIDE_FRONT:			copyv3 (v, newv[0][newc[0]]);			newc[0]++;			break;		case SIDE_BACK:			copyv3 (v, newv[1][newc[1]]);			newc[1]++;			break;		case SIDE_ON:			copyv3 (v, newv[0][newc[0]]);			newc[0]++;			copyv3 (v, newv[1][newc[1]]);			newc[1]++;			break;		}		if(sides[i] == SIDE_ON || sides[i+1] == SIDE_ON || sides[i+1] == sides[i])			continue;		d = dists[i] / (dists[i] - dists[i+1]);		for(j=0; j<3; j++){			e = v[j] + d*(v[j+3] - v[j]);			newv[0][newc[0]][j] = e;			newv[1][newc[1]][j] = e;		}		newc[0]++;		newc[1]++;	}	/* continue */	ClipSkyPolygon (newc[0], newv[0][0], stage+1);	ClipSkyPolygon (newc[1], newv[1][0], stage+1);}