From bbeaea1ea75ef466b2f0e08b433af43bb8d89f45 Mon Sep 17 00:00:00 2001
From: Rachael Alexanderson <18584402+madame-rachelle@users.noreply.github.com>
Date: Sun, 29 Sep 2024 18:09:07 -0400
Subject: [PATCH] - implement anamorphesis proof-of-concept (#2431)

Co-authored-by: Rachael Alexanderson <madame-rachelle@users.noreply.github.com>
---
 src/rendering/hwrenderer/scene/hw_sprites.cpp | 53 +++++++++++++++++++
 wadsrc/static/menudef.txt                     |  1 +
 2 files changed, 54 insertions(+)

diff --git a/src/rendering/hwrenderer/scene/hw_sprites.cpp b/src/rendering/hwrenderer/scene/hw_sprites.cpp
index 70da581cbe..61c120f31e 100644
--- a/src/rendering/hwrenderer/scene/hw_sprites.cpp
+++ b/src/rendering/hwrenderer/scene/hw_sprites.cpp
@@ -81,6 +81,8 @@ EXTERN_CVAR(Float, r_actorspriteshadowfadeheight)
 CVAR(Bool, gl_usecolorblending, true, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
 CVAR(Bool, gl_sprite_blend, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG);
 CVAR(Int, gl_spriteclip, 1, CVAR_ARCHIVE)
+CVAR(Bool, r_debug_nolimitanamorphoses, false, 0)
+CVAR(Float, r_spriteclipanamorphicminbias, 0.6, CVAR_ARCHIVE)
 CVAR(Float, gl_sclipthreshold, 10.0, CVAR_ARCHIVE)
 CVAR(Float, gl_sclipfactor, 1.8f, CVAR_ARCHIVE)
 CVAR(Int, gl_particles_style, 2, CVAR_ARCHIVE | CVAR_GLOBALCONFIG) // 0 = square, 1 = round, 2 = smooth
@@ -1117,6 +1119,56 @@ void HWSprite::Process(HWDrawInfo *di, AActor* thing, sector_t * sector, area_t
 	if(thing->renderflags2 & RF2_ISOMETRICSPRITES) depth = depth * vp.PitchCos - vp.PitchSin * z2; // Helps with stacking actors with small xy offsets
 	if (isSpriteShadow) depth += 1.f/65536.f; // always sort shadows behind the sprite.
 
+	if (gl_spriteclip == -1 && (thing->renderflags & RF_SPRITETYPEMASK) == RF_FACESPRITE) // perform anamorphosis
+	{
+		float minbias = r_spriteclipanamorphicminbias;
+		minbias = clamp(minbias, 0.3f, 1.0f);
+
+		float btm = thing->Sector->floorplane.ZatPoint(thing) - thing->Floorclip;
+		float top = thing->Sector->ceilingplane.ZatPoint(thingpos);
+
+		float vbtm = thing->Sector->floorplane.ZatPoint(vp.Pos);
+		float vtop = thing->Sector->ceilingplane.ZatPoint(vp.Pos);
+
+		float vpx = vp.Pos.X;
+		float vpy = vp.Pos.Y;
+		float vpz = vp.Pos.Z;
+
+		float tpx = thingpos.X;
+		float tpy = thingpos.Y;
+		float tpz = thingpos.Z;
+
+		if (!(r_debug_nolimitanamorphoses))
+		{
+			// this should help prevent clipping through walls ...
+			float objradiusbias = 1.f - thing->radius / sqrt((vpx - tpx) * (vpx - tpx) + (vpy - tpy) * (vpy - tpy));
+			minbias = max(minbias, objradiusbias);
+		}
+
+		float bintersect, tintersect;
+		if (z2 < vpz && vbtm < vpz)
+			bintersect = min((btm - vpz) / (z2 - vpz), (vbtm - vpz) / (z2 - vpz));
+		else
+			bintersect = 1.0;
+
+		if (z1 > vpz && vtop > vpz)
+			tintersect = min((top - vpz) / (z1 - vpz), (vtop - vpz) / (z1 - vpz));
+		else
+			tintersect = 1.0;
+
+		if (thing->waterlevel >= 1 && thing->waterlevel <= 2)
+			bintersect = tintersect = 1.0f;
+
+		float spbias = clamp(min(bintersect, tintersect), minbias, 1.0f);
+		float vpbias = 1.0 - spbias;
+		x1 = x1 * spbias + vpx * vpbias;
+		y1 = y1 * spbias + vpy * vpbias;
+		z1 = z1 * spbias + vpz * vpbias;
+		x2 = x2 * spbias + vpx * vpbias;
+		y2 = y2 * spbias + vpy * vpbias;
+		z2 = z2 * spbias + vpz * vpbias;		
+	}
+
 	// light calculation
 
 	bool enhancedvision = false;
@@ -1335,6 +1387,7 @@ void HWSprite::Process(HWDrawInfo *di, AActor* thing, sector_t * sector, area_t
 	{
 		lightlist = nullptr;
 	}
+
 	PutSprite(di, hw_styleflags != STYLEHW_Solid);
 	rendered_sprites++;
 }
diff --git a/wadsrc/static/menudef.txt b/wadsrc/static/menudef.txt
index 0d099afb67..4ac0a00ff2 100644
--- a/wadsrc/static/menudef.txt
+++ b/wadsrc/static/menudef.txt
@@ -2392,6 +2392,7 @@ OptionValue "SpriteclipModes"
 	1, "$OPTVAL_SMART"
 	2, "$OPTVAL_ALWAYS"
 	3, "$OPTVAL_SMARTER"
+	-1, "$OPTVAL_ANAMORPHIC"
 }
 
 OptionValue "EnhancedStealth"