DoomRTX/neo/engine/models/ModelDecal.cpp

/*
===========================================================================

IceTech GPL Source Code
Copyright (C) 2026 Justin Marshall

This file is part of the IceTech GPL Source Code (?IceTech Source Code?).

IceTech Source Code is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

IceTech Source Code is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with IceTech Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the IceTech Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the IceTech Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing Justin Marshall, justinmarshall20@gmail.com

===========================================================================
*/

#include "precompiled.h"
#pragma hdrstop

#include "../renderer/tr_local.h"
#include "Model_local.h"

// decalFade	filter 5 0.1
// polygonOffset
// {
// map invertColor( textures/splat )
// blend GL_ZERO GL_ONE_MINUS_SRC
// vertexColor
// clamp
// }

#ifdef QUAKE4
int idRenderModelDecal::allocatedDecalCount = 0;
#endif

/*
==================
idRenderModelDecal::idRenderModelDecal
==================
*/
idRenderModelDecal::idRenderModelDecal(void) {
	memset(&tri, 0, sizeof(tri));
	tri.verts = verts;
	tri.indexes = indexes;
	material = NULL;
	nextDecal = NULL;
#ifdef QUAKE4
	memset(vertLifeSpan, 0, sizeof(vertLifeSpan));
#endif
}

/*
==================
idRenderModelDecal::~idRenderModelDecal
==================
*/
idRenderModelDecal::~idRenderModelDecal(void) {
}

/*
==================
idRenderModelDecal::Alloc
==================
*/
idRenderModelDecal* idRenderModelDecal::Alloc(void) {
#ifdef QUAKE4
	allocatedDecalCount++;
#endif
	return new idRenderModelDecal;
}

/*
==================
idRenderModelDecal::Free
==================
*/
void idRenderModelDecal::Free(idRenderModelDecal* decal) {
	if (decal == NULL) {
		return;
	}
#ifdef QUAKE4
	allocatedDecalCount--;
#endif
	delete decal;
}

/*
=================
idRenderModelDecal::CreateProjectionInfo
=================
*/
bool idRenderModelDecal::CreateProjectionInfo(decalProjectionInfo_t& info, const idFixedWinding& winding, const idVec3& projectionOrigin, const bool parallel, const float fadeDepth, const idMaterial* material, const int startTime) {

	if (winding.GetNumPoints() != NUM_DECAL_BOUNDING_PLANES - 2) {
		common->Printf("idRenderModelDecal::CreateProjectionInfo: winding must have %d points\n", NUM_DECAL_BOUNDING_PLANES - 2);
		return false;
	}

	assert(material != NULL);

	info.projectionOrigin = projectionOrigin;
	info.material = material;
	info.parallel = parallel;
	info.fadeDepth = fadeDepth;
	info.startTime = startTime;
#ifdef QUAKE4
	info.maxAngle = material->GetDecalInfo().maxAngle;
#endif
	info.force = false;

	// get the winding plane and the depth of the projection volume
	idPlane windingPlane;
	winding.GetPlane(windingPlane);
	float depth = windingPlane.Distance(projectionOrigin);

	// find the bounds for the projection
	winding.GetBounds(info.projectionBounds);
#ifdef QUAKE4
	if (parallel) {
		const idVec3 depthOffset = windingPlane.Normal() * depth;
		const idVec3 fadeOffset = windingPlane.Normal() * fadeDepth;
		for (int i = 0; i < winding.GetNumPoints(); i++) {
			const idVec3 p = winding[i].ToVec3();
			info.projectionBounds.AddPoint(p + depthOffset);
			info.projectionBounds.AddPoint(p - fadeOffset);
		}
	}
	else {
		info.projectionBounds.AddPoint(projectionOrigin);
	}
#else
	if (parallel) {
		info.projectionBounds.ExpandSelf(depth);
	}
	else {
		info.projectionBounds.AddPoint(projectionOrigin);
	}
#endif

	// calculate the world space projection volume bounding planes, positive sides face outside the decal
	if (parallel) {
		for (int i = 0; i < winding.GetNumPoints(); i++) {
			idVec3 edge = winding[(i + 1) % winding.GetNumPoints()].ToVec3() - winding[i].ToVec3();
			info.boundingPlanes[i].Normal().Cross(windingPlane.Normal(), edge);
			info.boundingPlanes[i].Normalize();
			info.boundingPlanes[i].FitThroughPoint(winding[i].ToVec3());
		}
	}
	else {
		for (int i = 0; i < winding.GetNumPoints(); i++) {
			info.boundingPlanes[i].FromPoints(projectionOrigin, winding[i].ToVec3(), winding[(i + 1) % winding.GetNumPoints()].ToVec3());
		}
	}
	info.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 2] = windingPlane;
	info.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 2][3] -= depth;
	info.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 1] = -windingPlane;

	// fades will be from these plane
	info.fadePlanes[0] = windingPlane;
	info.fadePlanes[0][3] -= fadeDepth;
	info.fadePlanes[1] = -windingPlane;
	info.fadePlanes[1][3] += depth - fadeDepth;

	// calculate the texture vectors for the winding
	float	len, texArea, inva;
	idVec3	temp;
	idVec5	d0, d1;

	const idVec5& a = winding[0];
	const idVec5& b = winding[1];
	const idVec5& c = winding[2];

	d0 = b.ToVec3() - a.ToVec3();
	d0.s = b.s - a.s;
	d0.t = b.t - a.t;
	d1 = c.ToVec3() - a.ToVec3();
	d1.s = c.s - a.s;
	d1.t = c.t - a.t;

	texArea = (d0[3] * d1[4]) - (d0[4] * d1[3]);
	if (texArea == 0.0f) {
		return false;
	}
	inva = 1.0f / texArea;

	temp[0] = (d0[0] * d1[4] - d0[4] * d1[0]) * inva;
	temp[1] = (d0[1] * d1[4] - d0[4] * d1[1]) * inva;
	temp[2] = (d0[2] * d1[4] - d0[4] * d1[2]) * inva;
	len = temp.Normalize();
	if (len == 0.0f) {
		return false;
	}
	info.textureAxis[0].Normal() = temp * (1.0f / len);
	info.textureAxis[0][3] = winding[0].s - (winding[0].ToVec3() * info.textureAxis[0].Normal());

	temp[0] = (d0[3] * d1[0] - d0[0] * d1[3]) * inva;
	temp[1] = (d0[3] * d1[1] - d0[1] * d1[3]) * inva;
	temp[2] = (d0[3] * d1[2] - d0[2] * d1[3]) * inva;
	len = temp.Normalize();
	if (len == 0.0f) {
		return false;
	}
	info.textureAxis[1].Normal() = temp * (1.0f / len);
	info.textureAxis[1][3] = winding[0].t - (winding[0].ToVec3() * info.textureAxis[1].Normal());

	return true;
}

/*
=================
idRenderModelDecal::GlobalProjectionInfoToLocal
=================
*/
void idRenderModelDecal::GlobalProjectionInfoToLocal(decalProjectionInfo_t& localInfo, const decalProjectionInfo_t& info, const idVec3& origin, const idMat3& axis) {
	float modelMatrix[16];

	R_AxisToModelMatrix(axis, origin, modelMatrix);

	for (int j = 0; j < NUM_DECAL_BOUNDING_PLANES; j++) {
		R_GlobalPlaneToLocal(modelMatrix, info.boundingPlanes[j], localInfo.boundingPlanes[j]);
	}
	R_GlobalPlaneToLocal(modelMatrix, info.fadePlanes[0], localInfo.fadePlanes[0]);
	R_GlobalPlaneToLocal(modelMatrix, info.fadePlanes[1], localInfo.fadePlanes[1]);
	R_GlobalPlaneToLocal(modelMatrix, info.textureAxis[0], localInfo.textureAxis[0]);
	R_GlobalPlaneToLocal(modelMatrix, info.textureAxis[1], localInfo.textureAxis[1]);
	R_GlobalPointToLocal(modelMatrix, info.projectionOrigin, localInfo.projectionOrigin);
	localInfo.projectionBounds = info.projectionBounds;
	localInfo.projectionBounds.TranslateSelf(-origin);
	localInfo.projectionBounds.RotateSelf(axis.Transpose());
	localInfo.material = info.material;
	localInfo.parallel = info.parallel;
	localInfo.fadeDepth = info.fadeDepth;
	localInfo.startTime = info.startTime;
#ifdef QUAKE4
	localInfo.maxAngle = info.maxAngle;
#endif
	localInfo.force = info.force;
}

/*
=================
idRenderModelDecal::AddWinding
=================
*/
void idRenderModelDecal::AddWinding(const idWinding& w, const idMaterial* decalMaterial, const idPlane fadePlanes[2], float fadeDepth, int startTime) {
	int i;
	float invFadeDepth, fade;
#ifndef QUAKE4
	decalInfo_t	decalInfo;
#endif

	if ((material == NULL || material == decalMaterial) &&
		tri.numVerts + w.GetNumPoints() < MAX_DECAL_VERTS &&
		tri.numIndexes + (w.GetNumPoints() - 2) * 3 < MAX_DECAL_INDEXES) {

		material = decalMaterial;

		// add to this decal
#ifndef QUAKE4
		decalInfo = material->GetDecalInfo();
#endif
		invFadeDepth = -1.0f / fadeDepth;

		for (i = 0; i < w.GetNumPoints(); i++) {
			fade = fadePlanes[0].Distance(w[i].ToVec3()) * invFadeDepth;
			if (fade < 0.0f) {
				fade = fadePlanes[1].Distance(w[i].ToVec3()) * invFadeDepth;
			}
			if (fade < 0.0f) {
				fade = 0.0f;
			}
			else if (fade > 0.99f) {
				fade = 1.0f;
			}
			fade = 1.0f - fade;
			vertDepthFade[tri.numVerts + i] = fade;
#ifdef QUAKE4
			vertLifeSpan[tri.numVerts + i] = 0.0f;
#endif
			tri.verts[tri.numVerts + i].xyz = w[i].ToVec3();
			tri.verts[tri.numVerts + i].st[0] = w[i].s;
			tri.verts[tri.numVerts + i].st[1] = w[i].t;
#ifndef QUAKE4
			for (int k = 0; k < 4; k++) {
				int icolor = idMath::FtoiFast(decalInfo.start[k] * fade * 255.0f);
				if (icolor < 0) {
					icolor = 0;
				}
				else if (icolor > 255) {
					icolor = 255;
				}
				tri.verts[tri.numVerts + i].color[k] = icolor;
			}
#else
			// Quake 4 decal color is evaluated through material stages later.
			// Do not use decalInfo.start/end here because Q4 decalInfo_t does not have them.
			tri.verts[tri.numVerts + i].color[0] = 255;
			tri.verts[tri.numVerts + i].color[1] = 255;
			tri.verts[tri.numVerts + i].color[2] = 255;
			tri.verts[tri.numVerts + i].color[3] = 255;
#endif
		}
		for (i = 2; i < w.GetNumPoints(); i++) {
			tri.indexes[tri.numIndexes + 0] = tri.numVerts;
			tri.indexes[tri.numIndexes + 1] = tri.numVerts + i - 1;
			tri.indexes[tri.numIndexes + 2] = tri.numVerts + i;
			indexStartTime[tri.numIndexes] =
				indexStartTime[tri.numIndexes + 1] =
#ifdef QUAKE4
				indexStartTime[tri.numIndexes + 2] = (float)startTime;
#else
				indexStartTime[tri.numIndexes + 2] = startTime;
#endif
			tri.numIndexes += 3;
		}
		tri.numVerts += w.GetNumPoints();
		return;
	}

	// if we are at the end of the list, create a new decal
	if (!nextDecal) {
		nextDecal = idRenderModelDecal::Alloc();
	}
	// let the next decal on the chain take a look
	nextDecal->AddWinding(w, decalMaterial, fadePlanes, fadeDepth, startTime);
}

/*
=================
idRenderModelDecal::AddDepthFadedWinding
=================
*/
void idRenderModelDecal::AddDepthFadedWinding(const idWinding& w, const idMaterial* decalMaterial, const idPlane fadePlanes[2], float fadeDepth, int startTime) {
	idFixedWinding front, back;

	front = w;
	if (front.Split(&back, fadePlanes[0], 0.1f) == SIDE_CROSS) {
		AddWinding(back, decalMaterial, fadePlanes, fadeDepth, startTime);
	}

	if (front.Split(&back, fadePlanes[1], 0.1f) == SIDE_CROSS) {
		AddWinding(back, decalMaterial, fadePlanes, fadeDepth, startTime);
	}

	AddWinding(front, decalMaterial, fadePlanes, fadeDepth, startTime);
}

/*
=================
idRenderModelDecal::CreateDecal
=================
*/
void idRenderModelDecal::CreateDecal(const idRenderModel* model, const decalProjectionInfo_t& localInfo) {

	// check all model surfaces
	for (int surfNum = 0; surfNum < model->NumSurfaces(); surfNum++) {
		const modelSurface_t* surf = model->Surface(surfNum);

		// if no geometry or no shader
		if (!surf->geometry || !surf->shader) {
			continue;
		}

		// decals and overlays use the same rules
		if (!localInfo.force && !surf->shader->AllowOverlays()) {
			continue;
		}

		srfTriangles_t* stri = surf->geometry;

		// if the triangle bounds do not overlap with projection bounds
		if (!localInfo.projectionBounds.IntersectsBounds(stri->bounds)) {
			continue;
		}

		// allocate memory for the cull bits
		byte* cullBits = (byte*)_alloca16(stri->numVerts * sizeof(cullBits[0]));

		// categorize all points by the planes
		SIMDProcessor->DecalPointCull(cullBits, localInfo.boundingPlanes, stri->verts, stri->numVerts);

		// find triangles inside the projection volume
		for (int triNum = 0, index = 0; index < stri->numIndexes; index += 3, triNum++) {
			int v1 = stri->indexes[index + 0];
			int v2 = stri->indexes[index + 1];
			int v3 = stri->indexes[index + 2];

			// skip triangles completely off one side
			if (cullBits[v1] & cullBits[v2] & cullBits[v3]) {
				continue;
			}

			// skip back facing triangles
			if (stri->facePlanes && stri->facePlanesCalculated) {
#ifdef QUAKE4
				if (stri->facePlanes[triNum].Normal() * localInfo.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 2].Normal() < localInfo.maxAngle) {
					continue;
				}
#else
				if (stri->facePlanes[triNum].Normal() * localInfo.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 2].Normal() < -0.1f) {
					continue;
				}
#endif
			}

			// create a winding with texture coordinates for the triangle
			idFixedWinding fw;
			fw.SetNumPoints(3);
			if (localInfo.parallel) {
				for (int j = 0; j < 3; j++) {
					fw[j] = stri->verts[stri->indexes[index + j]].xyz;
					fw[j].s = localInfo.textureAxis[0].Distance(fw[j].ToVec3());
					fw[j].t = localInfo.textureAxis[1].Distance(fw[j].ToVec3());
				}
			}
			else {
				for (int j = 0; j < 3; j++) {
					idVec3 dir;
					float scale;

					fw[j] = stri->verts[stri->indexes[index + j]].xyz;
					dir = fw[j].ToVec3() - localInfo.projectionOrigin;
					localInfo.boundingPlanes[NUM_DECAL_BOUNDING_PLANES - 1].RayIntersection(fw[j].ToVec3(), dir, scale);
					dir = fw[j].ToVec3() + scale * dir;
					fw[j].s = localInfo.textureAxis[0].Distance(dir);
					fw[j].t = localInfo.textureAxis[1].Distance(dir);
				}
			}

			int orBits = cullBits[v1] | cullBits[v2] | cullBits[v3];

			// clip the exact surface triangle to the projection volume
			for (int j = 0; j < NUM_DECAL_BOUNDING_PLANES; j++) {
				if (orBits & (1 << j)) {
					if (!fw.ClipInPlace(-localInfo.boundingPlanes[j])) {
						break;
					}
				}
			}

			if (fw.GetNumPoints() == 0) {
				continue;
			}

			AddDepthFadedWinding(fw, localInfo.material, localInfo.fadePlanes, localInfo.fadeDepth, localInfo.startTime);
		}
	}
}

/*
=====================
idRenderModelDecal::RemoveFadedDecals
=====================
*/
idRenderModelDecal* idRenderModelDecal::RemoveFadedDecals(idRenderModelDecal* decals, int time) {
	int i, j, newNumIndexes, newNumVerts;
	int inUse[MAX_DECAL_VERTS];
	decalInfo_t	decalInfo;
	idRenderModelDecal* nextDecal;

	if (decals == NULL) {
		return NULL;
	}

	// recursively free any next decals
	decals->nextDecal = RemoveFadedDecals(decals->nextDecal, time);

	// free the decals if no material set
	if (decals->material == NULL) {
		nextDecal = decals->nextDecal;
		Free(decals);
		return nextDecal;
	}

	decalInfo = decals->material->GetDecalInfo();

#ifdef QUAKE4
	const float minTime = (float)(time - decalInfo.stayTime);
#else
	const int minTime = time - (decalInfo.stayTime + decalInfo.fadeTime);
#endif

	newNumIndexes = 0;
	for (i = 0; i < decals->tri.numIndexes; i += 3) {
		if (decals->indexStartTime[i] > minTime) {
			// keep this triangle
			if (newNumIndexes != i) {
				for (j = 0; j < 3; j++) {
					decals->tri.indexes[newNumIndexes + j] = decals->tri.indexes[i + j];
					decals->indexStartTime[newNumIndexes + j] = decals->indexStartTime[i + j];
				}
			}
			newNumIndexes += 3;
		}
	}

	// free the decals if all triangles faded away
	if (newNumIndexes == 0) {
		nextDecal = decals->nextDecal;
		Free(decals);
		return nextDecal;
	}

	decals->tri.numIndexes = newNumIndexes;

	memset(inUse, 0, sizeof(inUse));
	for (i = 0; i < decals->tri.numIndexes; i++) {
		inUse[decals->tri.indexes[i]] = 1;
	}

	newNumVerts = 0;
	for (i = 0; i < decals->tri.numVerts; i++) {
		if (!inUse[i]) {
			continue;
		}
		decals->tri.verts[newNumVerts] = decals->tri.verts[i];
		decals->vertDepthFade[newNumVerts] = decals->vertDepthFade[i];
#ifdef QUAKE4
		decals->vertLifeSpan[newNumVerts] = decals->vertLifeSpan[i];
#endif
		inUse[i] = newNumVerts;
		newNumVerts++;
	}
	decals->tri.numVerts = newNumVerts;

	for (i = 0; i < decals->tri.numIndexes; i++) {
		decals->tri.indexes[i] = inUse[decals->tri.indexes[i]];
	}

	return decals;
}

/*
=====================
idRenderModelDecal::AddDecalDrawSurf
=====================
*/
void idRenderModelDecal::AddDecalDrawSurf(viewEntity_t* space) {
	int i, j, maxTime;
	float f;
	decalInfo_t	decalInfo;


	if (tri.numIndexes == 0) {
		return;
	}

	// fade down all the verts with time
	decalInfo = material->GetDecalInfo();
#ifdef QUAKE4
	maxTime = decalInfo.stayTime;
#else
	maxTime = decalInfo.stayTime + decalInfo.fadeTime;
#endif

	// set vertex colors and remove faded triangles
	for (i = 0; i < tri.numIndexes; i += 3) {
#ifdef QUAKE4
		float deltaTime = (float)tr.viewDef->renderView.time - indexStartTime[i];

		if (deltaTime > maxTime) {
			continue;
		}
		if (deltaTime < 0.0f) {
			deltaTime = 0.0f;
		}

		f = (maxTime > 0) ? deltaTime / (float)maxTime : 1.0f;
		for (j = 0; j < 3; j++) {
			vertLifeSpan[tri.indexes[i + j]] = f;
		}
#else
		int	deltaTime = tr.viewDef->renderView.time - indexStartTime[i];

		if (deltaTime > maxTime) {
			continue;
		}

		if (deltaTime <= decalInfo.stayTime) {
			continue;
		}

		deltaTime -= decalInfo.stayTime;
		f = (float)deltaTime / decalInfo.fadeTime;

		for (j = 0; j < 3; j++) {
			int	ind = tri.indexes[i + j];

			for (int k = 0; k < 4; k++) {
				float fcolor = decalInfo.start[k] + (decalInfo.end[k] - decalInfo.start[k]) * f;
				int icolor = idMath::FtoiFast(fcolor * vertDepthFade[ind] * 255.0f);
				if (icolor < 0) {
					icolor = 0;
				}
				else if (icolor > 255) {
					icolor = 255;
				}
				tri.verts[ind].color[k] = icolor;
			}
		}
#endif
	}

#ifdef QUAKE4
	// Q4 stores decal age in vertLifeSpan.  The material stage path can consume that
	// when you wire Q4's stage-register/color-cache code in.  Do not reference
	// decalInfo.start/end here; Q4 decalInfo_t does not define those members.
#endif

	// copy the tri and indexes to temp heap memory,
	// because if we are running multi-threaded, we wouldn't
	// be able to reorganize the index list
	srfTriangles_t* newTri = (srfTriangles_t*)R_FrameAlloc(sizeof(*newTri));
	*newTri = tri;

	// copy the current vertexes to temp vertex cache
	newTri->ambientCache = vertexCache.AllocFrameTemp(tri.verts, tri.numVerts * sizeof(idDrawVert));

	// create the drawsurf
	R_AddDrawSurf(newTri, space, &space->entityDef->parms, material, space->scissorRect);
}

/*
====================
idRenderModelDecal::ReadFromDemoFile
====================
*/
void idRenderModelDecal::ReadFromDemoFile(idDemoFile* f) {
	// FIXME: implement
}

/*
====================
idRenderModelDecal::WriteToDemoFile
====================
*/
void idRenderModelDecal::WriteToDemoFile(idDemoFile* f) const {
	// FIXME: implement
}