gzdoom-gles/src/swrenderer/scene/r_light.h

//
// Copyright (C) 1993-1996 by id Software, Inc.
//
// This source is available for distribution and/or modification
// only under the terms of the DOOM Source Code License as
// published by id Software. All rights reserved.
//
// The source is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
// for more details.
//

#pragma once

#include <stddef.h>
#include "r_defs.h"
#include "v_palette.h"
#include "r_data/colormaps.h"
#include "r_utility.h"

// Lighting.
//
// [RH] This has changed significantly from Doom, which used lookup
// tables based on 1/z for walls and z for flats and only recognized
// 16 discrete light levels. The terminology I use is borrowed from Build.

// The size of a single colormap, in bits
#define COLORMAPSHIFT 8

// Convert a light level into an unbounded colormap index (shade). Result is
// fixed point. Why the +12? I wish I knew, but experimentation indicates it
// is necessary in order to best reproduce Doom's original lighting.
#define LIGHT2SHADE(l) ((NUMCOLORMAPS*2*FRACUNIT)-(((l)+12)*(FRACUNIT*NUMCOLORMAPS/128)))

// MAXLIGHTSCALE from original DOOM, divided by 2.
#define MAXLIGHTVIS (24.0)

// Convert a shade and visibility to a clamped colormap index.
// Result is not fixed point.
// Change R_CalcTiltedLighting() when this changes.
#define GETPALOOKUP(vis,shade) (clamp<int> (((shade)-FLOAT2FIXED(MIN(MAXLIGHTVIS,double(vis))))>>FRACBITS, 0, NUMCOLORMAPS-1))

// Calculate the light multiplier for dc_light/ds_light
// This is used instead of GETPALOOKUP when ds_colormap/dc_colormap is set to the base colormap
// Returns a value between 0 and 1 in fixed point
#define LIGHTSCALE(vis,shade) FLOAT2FIXED(clamp((FIXED2DBL(shade) - (MIN(MAXLIGHTVIS,double(vis)))) / NUMCOLORMAPS, 0.0, (NUMCOLORMAPS-1)/(double)NUMCOLORMAPS))

// Converts fixedlightlev into a shade value
#define FIXEDLIGHT2SHADE(lightlev) (((lightlev) >> COLORMAPSHIFT) << FRACBITS)

struct FSWColormap;

namespace swrenderer
{
	extern double r_BaseVisibility;
	extern double r_WallVisibility;
	extern double r_FloorVisibility;
	extern float r_TiltVisibility;
	extern double r_SpriteVisibility;

	extern int fixedlightlev;
	extern FSWColormap *fixedcolormap;
	extern FSpecialColormap *realfixedcolormap;

	inline int R_ActualExtraLight(bool fog) { return fog ? 0 : extralight << 4; }

	void R_SetVisibility(double visibility);
	double R_GetVisibility();

	void R_SetupColormap(AActor *actor);

	class ColormapLight
	{
	public:
		int ColormapNum = 0;
		FSWColormap *BaseColormap = nullptr;

		void SetColormap(double visibility, int shade, FDynamicColormap *basecolormap, bool fullbright, bool invertColormap, bool fadeToBlack);
	};
}