DoomRTX/neo/engine/renderer/tr_backend.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 "tr_local.h"


frameData_t		*frameData;
backEndState_t	backEnd;


/*
======================
RB_SetDefaultGLState

This should initialize all GL state that any part of the entire program
may touch, including the editor.
======================
*/
void RB_SetDefaultGLState( void ) {
	int		i;

	RB_LogComment( "--- R_SetDefaultGLState ---\n" );

	glClearDepth( 1.0f );
	glColor4f (1,1,1,1);

	// the vertex array is always enabled
	glEnableClientState( GL_VERTEX_ARRAY );
	glEnableClientState( GL_TEXTURE_COORD_ARRAY );
	glDisableClientState( GL_COLOR_ARRAY );

	//
	// make sure our GL state vector is set correctly
	//
	memset( &backEnd.glState, 0, sizeof( backEnd.glState ) );
	backEnd.glState.forceGlState = true;

	glColorMask( 1, 1, 1, 1 );

	glEnable( GL_DEPTH_TEST );
	glEnable( GL_BLEND );
	glEnable( GL_SCISSOR_TEST );
	glEnable( GL_CULL_FACE );
	glDisable( GL_LIGHTING );
	glDisable( GL_FOG );
	glDisable( GL_LINE_STIPPLE );
	glDisable( GL_STENCIL_TEST );

	glPolygonMode (GL_FRONT_AND_BACK, GL_FILL);
	glDepthMask( GL_TRUE );
	glDepthFunc( GL_ALWAYS );
 
	glCullFace( GL_FRONT_AND_BACK );
	glShadeModel( GL_SMOOTH );

	if ( r_useScissor.GetBool() ) {
		glScissor( 0, 0, glConfig.vidWidth, glConfig.vidHeight );
	}

	for ( i = glConfig.maxTextureUnits - 1 ; i >= 0 ; i-- ) {
		GL_SelectTexture( i );

		// object linear texgen is our default
		glTexGenf( GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
		glTexGenf( GL_T, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
		glTexGenf( GL_R, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );
		glTexGenf( GL_Q, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR );

		GL_TexEnv( GL_MODULATE );
		glDisable( GL_TEXTURE_2D );
		if ( glConfig.texture3DAvailable ) {
			glDisable( GL_TEXTURE_3D );
		}
		if ( glConfig.cubeMapAvailable ) {
			glDisable( GL_TEXTURE_CUBE_MAP_EXT );
		}
	}
}


/*
====================
RB_LogComment
====================
*/
void RB_LogComment( const char *comment, ... ) {
   va_list marker;

	if ( !tr.logFile ) {
		return;
	}

	fprintf( tr.logFile, "// " );
	va_start( marker, comment );
	vfprintf( tr.logFile, comment, marker );
	va_end( marker );
}


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



/*
====================
GL_SelectTexture
====================
*/
void GL_SelectTexture( int unit ) {
	if ( backEnd.glState.currenttmu == unit ) {
		return;
	}

	if ( unit < 0 || unit >= glConfig.maxTextureUnits && unit >= glConfig.maxTextureImageUnits ) {
		common->Warning( "GL_SelectTexture: unit = %i", unit );
		return;
	}

	glActiveTextureARB( GL_TEXTURE0_ARB + unit );
	glClientActiveTextureARB( GL_TEXTURE0_ARB + unit );
	RB_LogComment( "glActiveTextureARB( %i );\nglClientActiveTextureARB( %i );\n", unit, unit );

	backEnd.glState.currenttmu = unit;
}


/*
====================
GL_Cull

This handles the flipping needed when the view being
rendered is a mirored view.
====================
*/
void GL_Cull( int cullType ) {
	if ( backEnd.glState.faceCulling == cullType ) {
		return;
	}

	if ( cullType == CT_TWO_SIDED ) {
		glDisable( GL_CULL_FACE );
	} else  {
		if ( backEnd.glState.faceCulling == CT_TWO_SIDED ) {
			glEnable( GL_CULL_FACE );
		}

		if ( cullType == CT_BACK_SIDED ) {
			if ( backEnd.viewDef->isMirror ) {
				glCullFace( GL_FRONT );
			} else {
				glCullFace( GL_BACK );
			}
		} else {
			if ( backEnd.viewDef->isMirror ) {
				glCullFace( GL_BACK );
			} else {
				glCullFace( GL_FRONT );
			}
		}
	}

	backEnd.glState.faceCulling = cullType;
}

/*
====================
GL_TexEnv
====================
*/
void GL_TexEnv( int env ) {
	tmu_t	*tmu;

	tmu = &backEnd.glState.tmu[backEnd.glState.currenttmu];
	if ( env == tmu->texEnv ) {
		return;
	}

	tmu->texEnv = env;

	switch ( env ) {
	case GL_COMBINE_EXT:
	case GL_MODULATE:
	case GL_REPLACE:
	case GL_DECAL:
	case GL_ADD:
		glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, env );
		break;
	default:
		common->Error( "GL_TexEnv: invalid env '%d' passed\n", env );
		break;
	}
}

/*
=================
GL_ClearStateDelta

Clears the state delta bits, so the next GL_State
will set every item
=================
*/
void GL_ClearStateDelta( void ) {
	backEnd.glState.forceGlState = true;
}

/*
====================
GL_State

This routine is responsible for setting the most commonly changed state
====================
*/
void GL_State(int stateBits) {
	int	diff;

	if (!r_useStateCaching.GetBool() || backEnd.glState.forceGlState) {
		// make sure everything is set all the time, so we
		// can see if our delta checking is screwing up
		diff = -1;
		backEnd.glState.forceGlState = false;
	}
	else {
		diff = stateBits ^ backEnd.glState.glStateBits;
		if (!diff) {
			return;
		}
	}

	//
	// check depthFunc bits
	//
	if (diff & (GLS_DEPTHFUNC_EQUAL | GLS_DEPTHFUNC_LESS | GLS_DEPTHFUNC_ALWAYS)) {
		if (stateBits & GLS_DEPTHFUNC_EQUAL) {
			glDepthFunc(GL_EQUAL);
		}
		else if (stateBits & GLS_DEPTHFUNC_ALWAYS) {
			glDepthFunc(GL_ALWAYS);
		}
		else {
			glDepthFunc(GL_LEQUAL);
		}
	}


	//
	// check blend bits
	//
	if (diff & (GLS_SRCBLEND_BITS | GLS_DSTBLEND_BITS)) {
		GLenum srcFactor, dstFactor;

		switch (stateBits & GLS_SRCBLEND_BITS) {
		case GLS_SRCBLEND_ZERO:
			srcFactor = GL_ZERO;
			break;
		case GLS_SRCBLEND_ONE:
			srcFactor = GL_ONE;
			break;
		case GLS_SRCBLEND_DST_COLOR:
			srcFactor = GL_DST_COLOR;
			break;
		case GLS_SRCBLEND_ONE_MINUS_DST_COLOR:
			srcFactor = GL_ONE_MINUS_DST_COLOR;
			break;
		case GLS_SRCBLEND_SRC_COLOR:
			srcFactor = GL_SRC_COLOR;
			break;
		case GLS_SRCBLEND_ONE_MINUS_SRC_COLOR:
			srcFactor = GL_ONE_MINUS_SRC_COLOR;
			break;
		case GLS_SRCBLEND_SRC_ALPHA:
			srcFactor = GL_SRC_ALPHA;
			break;
		case GLS_SRCBLEND_ONE_MINUS_SRC_ALPHA:
			srcFactor = GL_ONE_MINUS_SRC_ALPHA;
			break;
		case GLS_SRCBLEND_DST_ALPHA:
			srcFactor = GL_DST_ALPHA;
			break;
		case GLS_SRCBLEND_ONE_MINUS_DST_ALPHA:
			srcFactor = GL_ONE_MINUS_DST_ALPHA;
			break;
		case GLS_SRCBLEND_ALPHA_SATURATE:
			srcFactor = GL_SRC_ALPHA_SATURATE;
			break;

		case GLS_DSTBLEND_DST_COLOR:
			dstFactor = GL_DST_COLOR;
			break;

		case GLS_DSTBLEND_ONE_MINUS_DST_COLOR:
			dstFactor = GL_ONE_MINUS_DST_COLOR;
			break;
		default:
			srcFactor = GL_ONE;		// to get warning to shut up
			common->Error("GL_State: invalid src blend state bits\n");
			break;
		}

		switch (stateBits & GLS_DSTBLEND_BITS) {
		case GLS_DSTBLEND_ZERO:
			dstFactor = GL_ZERO;
			break;
		case GLS_DSTBLEND_ONE:
			dstFactor = GL_ONE;
			break;
		case GLS_DSTBLEND_SRC_COLOR:
			dstFactor = GL_SRC_COLOR;
			break;
		case GLS_DSTBLEND_ONE_MINUS_SRC_COLOR:
			dstFactor = GL_ONE_MINUS_SRC_COLOR;
			break;
		case GLS_DSTBLEND_SRC_ALPHA:
			dstFactor = GL_SRC_ALPHA;
			break;
		case GLS_DSTBLEND_ONE_MINUS_SRC_ALPHA:
			dstFactor = GL_ONE_MINUS_SRC_ALPHA;
			break;
		case GLS_DSTBLEND_DST_ALPHA:
			dstFactor = GL_DST_ALPHA;
			break;
		case GLS_DSTBLEND_ONE_MINUS_DST_ALPHA:
			dstFactor = GL_ONE_MINUS_DST_ALPHA;
			break;
		default:
			dstFactor = GL_ONE;		// to get warning to shut up
			common->Error("GL_State: invalid dst blend state bits\n");
			break;
		}

		glBlendFunc(srcFactor, dstFactor);
	}

	//
	// check depthmask
	//
	if (diff & GLS_DEPTHMASK) {
		if (stateBits & GLS_DEPTHMASK) {
			glDepthMask(GL_FALSE);
		}
		else {
			glDepthMask(GL_TRUE);
		}
	}

	//
	// check colormask
	//
	if (diff & (GLS_REDMASK | GLS_GREENMASK | GLS_BLUEMASK | GLS_ALPHAMASK)) {
		GLboolean		r, g, b, a;
		r = (stateBits & GLS_REDMASK) ? 0 : 1;
		g = (stateBits & GLS_GREENMASK) ? 0 : 1;
		b = (stateBits & GLS_BLUEMASK) ? 0 : 1;
		a = (stateBits & GLS_ALPHAMASK) ? 0 : 1;
		glColorMask(r, g, b, a);
	}

	//
	// fill/line mode
	//
	if (diff & GLS_POLYMODE_LINE) {
		if (stateBits & GLS_POLYMODE_LINE) {
			glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
		}
		else {
			glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
		}
	}

	//
	// alpha test
	//
	if (diff & GLS_ATEST_BITS) {
		switch (stateBits & GLS_ATEST_BITS) {
		case 0:
			glDisable(GL_ALPHA_TEST);
			break;
		case GLS_ATEST_EQ_255:
			glEnable(GL_ALPHA_TEST);
			glAlphaFunc(GL_EQUAL, 1);
			break;
		case GLS_ATEST_LT_128:
			glEnable(GL_ALPHA_TEST);
			glAlphaFunc(GL_LESS, 0.5);
			break;
		case GLS_ATEST_GE_128:
			glEnable(GL_ALPHA_TEST);
			glAlphaFunc(GL_GEQUAL, 0.5);
			break;
		default:
			assert(0);
			break;
		}
	}

	backEnd.glState.glStateBits = stateBits;
}




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

RENDER BACK END THREAD FUNCTIONS

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

/*
=============
RB_SetGL2D

This is not used by the normal game paths, just by some tools
=============
*/
void RB_SetGL2D( void ) {
	// set 2D virtual screen size
	glViewport( 0, 0, glConfig.vidWidth, glConfig.vidHeight );
	if ( r_useScissor.GetBool() ) {
		glScissor( 0, 0, glConfig.vidWidth, glConfig.vidHeight );
	}
	glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
	glOrtho( 0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, 0, 1 );		// always assume 640x480 virtual coordinates
	glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

	GL_State( GLS_DEPTHFUNC_ALWAYS |
			  GLS_SRCBLEND_SRC_ALPHA |
			  GLS_DSTBLEND_ONE_MINUS_SRC_ALPHA );

	GL_Cull( CT_TWO_SIDED );

	glDisable( GL_DEPTH_TEST );
	glDisable( GL_STENCIL_TEST );
}



/*
=============
RB_SetBuffer

=============
*/
static void	RB_SetBuffer( const void *data ) {
	const setBufferCommand_t	*cmd;

	// see which draw buffer we want to render the frame to

	cmd = (const setBufferCommand_t *)data;

	backEnd.frameCount = cmd->frameCount;

	glDrawBuffer( cmd->buffer );

	// clear screen for debugging
	// automatically enable this with several other debug tools
	// that might leave unrendered portions of the screen
	if ( r_clear.GetFloat() || idStr::Length( r_clear.GetString() ) != 1 || r_lockSurfaces.GetBool() || r_singleArea.GetBool() || r_showOverDraw.GetBool() ) {
		float c[3];
		if ( sscanf( r_clear.GetString(), "%f %f %f", &c[0], &c[1], &c[2] ) == 3 ) {
			glClearColor( c[0], c[1], c[2], 1 );
		} else if ( r_clear.GetInteger() == 2 ) {
			glClearColor( 0.0f, 0.0f,  0.0f, 1.0f );
		} else if ( r_showOverDraw.GetBool() ) {
			glClearColor( 1.0f, 1.0f, 1.0f, 1.0f );
		} else {
			glClearColor( 0.4f, 0.0f, 0.25f, 1.0f );
		}
		glClear( GL_COLOR_BUFFER_BIT );
	}
}

/*
===============
RB_ShowImages

Draw all the images to the screen, on top of whatever
was there.  This is used to test for texture thrashing.
===============
*/
void RB_ShowImages( void ) {
	int		i;
	idImage	*image;
	float	x, y, w, h;
	int		start, end;

	RB_SetGL2D();

	//glClearColor( 0.2, 0.2, 0.2, 1 );
	//glClear( GL_COLOR_BUFFER_BIT );

	glFinish();

	start = Sys_Milliseconds();

	for ( i = 0 ; i < globalImages->images.Num() ; i++ ) {
		image = globalImages->images[i];

		if ( image->texnum == idImage::TEXTURE_NOT_LOADED && image->partialImage == NULL ) {
			continue;
		}

		w = glConfig.vidWidth / 20;
		h = glConfig.vidHeight / 15;
		x = i % 20 * w;
		y = i / 20 * h;

		// show in proportional size in mode 2
		if ( r_showImages.GetInteger() == 2 ) {
			w *= image->uploadWidth / 512.0f;
			h *= image->uploadHeight / 512.0f;
		}

		image->Bind();
		glBegin (GL_QUADS);
		glTexCoord2f( 0, 0 );
		glVertex2f( x, y );
		glTexCoord2f( 1, 0 );
		glVertex2f( x + w, y );
		glTexCoord2f( 1, 1 );
		glVertex2f( x + w, y + h );
		glTexCoord2f( 0, 1 );
		glVertex2f( x, y + h );
		glEnd();
	}

	glFinish();

	end = Sys_Milliseconds();
	common->Printf( "%i msec to draw all images\n", end - start );
}


/*
=============
RB_SwapBuffers

=============
*/
const void	RB_SwapBuffers( const void *data ) {
	// texture swapping test
	if ( r_showImages.GetInteger() != 0 ) {
		RB_ShowImages();
	}

	// force a gl sync if requested
	if ( r_finish.GetBool() ) {
		glFinish();
	}

    RB_LogComment( "***************** RB_SwapBuffers *****************\n\n\n" );

	// don't flip if drawing to front buffer
	if ( !r_frontBuffer.GetBool() ) {
	    GLimp_SwapBuffers();
	}
}

/*
=============
RB_CopyRender

Copy part of the current framebuffer to an image
=============
*/
const void	RB_CopyRender( const void *data ) {
	const copyRenderCommand_t	*cmd;

	cmd = (const copyRenderCommand_t *)data;

	if ( r_skipCopyTexture.GetBool() ) {
		return;
	}

    RB_LogComment( "***************** RB_CopyRender *****************\n" );

	if (cmd->image) {
		cmd->image->CopyFramebuffer( cmd->x, cmd->y, cmd->imageWidth, cmd->imageHeight, false );
	}
}

/*
====================
RB_ExecuteBackEndCommands

This function will be called syncronously if running without
smp extensions, or asyncronously by another thread.
====================
*/
int		backEndStartTime, backEndFinishTime;
void RB_ExecuteBackEndCommands( const emptyCommand_t *cmds ) {
	// r_debugRenderToTexture
	int	c_draw3d = 0, c_draw2d = 0, c_setBuffers = 0, c_swapBuffers = 0, c_copyRenders = 0;

	if ( cmds->commandId == RC_NOP && !cmds->next ) {
		return;
	}

	backEndStartTime = Sys_Milliseconds();
	int backendCpuNoSwap = 0;

	// needed for editor rendering
	RB_SetDefaultGLState();

	// upload any image loads that have completed
	globalImages->CompleteBackgroundImageLoads();

	for ( ; cmds ; cmds = (const emptyCommand_t *)cmds->next ) {
		const int commandStartTime = Sys_Milliseconds();
		const renderCommand_t commandId = cmds->commandId;
		switch ( commandId ) {
		case RC_NOP:
			break;
		case RC_DRAW_VIEW:
			RB_DrawView( cmds );
			if ( ((const drawSurfsCommand_t *)cmds)->viewDef->viewEntitys ) {
				c_draw3d++;
			}
			else {
				c_draw2d++;
			}
			break;
		case RC_SET_BUFFER:
			RB_SetBuffer( cmds );
			c_setBuffers++;
			break;
		case RC_SWAP_BUFFERS:
			RB_SwapBuffers( cmds );
			c_swapBuffers++;
			break;
		case RC_COPY_RENDER:
			RB_CopyRender( cmds );
			c_copyRenders++;
			break;
		default:
			common->Error( "RB_ExecuteBackEndCommands: bad commandId" );
			break;
		}
		if ( commandId != RC_SWAP_BUFFERS ) {
			backendCpuNoSwap += Sys_Milliseconds() - commandStartTime;
		}
	}

	// go back to the default texture so the editor doesn't mess up a bound image
	glBindTexture( GL_TEXTURE_2D, 0 );
	backEnd.glState.tmu[0].current2DMap = -1;

	// stop rendering on this thread
	backEndFinishTime = Sys_Milliseconds();
	backEnd.pc.msec = backEndFinishTime - backEndStartTime;
	backEnd.pc.cpuMsecNoSwap = backendCpuNoSwap;

	if ( r_debugRenderToTexture.GetInteger() == 1 ) {
		common->Printf( "3d: %i, 2d: %i, SetBuf: %i, SwpBuf: %i, CpyRenders: %i, CpyFrameBuf: %i\n", c_draw3d, c_draw2d, c_setBuffers, c_swapBuffers, c_copyRenders, backEnd.c_copyFrameBuffer );
		backEnd.c_copyFrameBuffer = 0;
	}
}