From a441cea35076b6ee4abe09c5e0f08c7d83b47af5 Mon Sep 17 00:00:00 2001
From: Rachael Alexanderson <raa-eruanna@users.noreply.github.com>
Date: Thu, 28 Dec 2017 11:04:43 -0500
Subject: [PATCH] - interpolate particles

---
 src/gl/scene/gl_sprite.cpp               | 14 +++++++++++---
 src/polyrenderer/scene/poly_particle.cpp |  5 ++++-
 src/swrenderer/things/r_particle.cpp     | 22 +++++++++++++++-------
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/src/gl/scene/gl_sprite.cpp b/src/gl/scene/gl_sprite.cpp
index a773373ef..edd0da1d9 100644
--- a/src/gl/scene/gl_sprite.cpp
+++ b/src/gl/scene/gl_sprite.cpp
@@ -40,6 +40,7 @@
 #include "events.h"
 #include "actorinlines.h"
 #include "r_data/r_vanillatrans.h"
+#include "i_time.h"
 
 #include "gl/system/gl_interface.h"
 #include "gl/system/gl_framebuffer.h"
@@ -1209,9 +1210,16 @@ void GLSprite::ProcessParticle (particle_t *particle, sector_t *sector)//, int s
 		}
 	}
 
-	x = particle->Pos.X;
-	y = particle->Pos.Y;
-	z = particle->Pos.Z;
+	double timefrac = r_viewpoint.TicFrac;
+	if (paused || bglobal.freeze)
+		timefrac = 0.;
+	float xvf = (particle->Vel.X) * timefrac;
+	float yvf = (particle->Vel.Y) * timefrac;
+	float zvf = (particle->Vel.Z) * timefrac;
+
+	x = float(particle->Pos.X) + xvf;
+	y = float(particle->Pos.Y) + yvf;
+	z = float(particle->Pos.Z) + zvf;
 	
 	float factor;
 	if (gl_particles_style == 1) factor = 1.3f / 7.f;
diff --git a/src/polyrenderer/scene/poly_particle.cpp b/src/polyrenderer/scene/poly_particle.cpp
index 6b5e1e9c5..0ab3beb22 100644
--- a/src/polyrenderer/scene/poly_particle.cpp
+++ b/src/polyrenderer/scene/poly_particle.cpp
@@ -34,7 +34,10 @@ EXTERN_CVAR(Int, gl_particles_style)
 
 void RenderPolyParticle::Render(PolyRenderThread *thread, const TriMatrix &worldToClip, const PolyClipPlane &clipPlane, particle_t *particle, subsector_t *sub, uint32_t stencilValue)
 {
-	DVector3 pos = particle->Pos;
+	double timefrac = r_viewpoint.TicFrac;
+	if (paused || bglobal.freeze)
+		timefrac = 0.;
+	DVector3 pos = particle->Pos + (particle->Vel * timefrac);
 	double psize = particle->size / 8.0;
 	double zpos = pos.Z;
 
diff --git a/src/swrenderer/things/r_particle.cpp b/src/swrenderer/things/r_particle.cpp
index 33d2a6d09..7c2d88f48 100644
--- a/src/swrenderer/things/r_particle.cpp
+++ b/src/swrenderer/things/r_particle.cpp
@@ -77,7 +77,15 @@ namespace swrenderer
 		double	 			xscale, yscale;
 		int 				x1, x2, y1, y2;
 		sector_t*			heightsec = NULL;
-		
+
+		double timefrac = r_viewpoint.TicFrac;
+		if (paused || bglobal.freeze)
+			timefrac = 0.;
+
+		double ippx = particle->Pos.X + particle->Vel.X * timefrac;
+		double ippy = particle->Pos.Y + particle->Vel.Y * timefrac;
+		double ippz = particle->Pos.Z + particle->Vel.Z * timefrac;
+
 		RenderPortal *renderportal = thread->Portal.get();
 
 		// [ZZ] Particle not visible through the portal plane
@@ -85,8 +93,8 @@ namespace swrenderer
 			return;
 
 		// transform the origin point
-		tr_x = particle->Pos.X - thread->Viewport->viewpoint.Pos.X;
-		tr_y = particle->Pos.Y - thread->Viewport->viewpoint.Pos.Y;
+		tr_x = ippx - thread->Viewport->viewpoint.Pos.X;
+		tr_y = ippy - thread->Viewport->viewpoint.Pos.Y;
 
 		tz = tr_x * thread->Viewport->viewpoint.TanCos + tr_y * thread->Viewport->viewpoint.TanSin;
 
@@ -121,7 +129,7 @@ namespace swrenderer
 		auto viewport = thread->Viewport.get();
 
 		yscale = xscale; // YaspectMul is not needed for particles as they should always be square
-		ty = (particle->Pos.Z - viewport->viewpoint.Pos.Z) * thread->Viewport->YaspectMul;
+		ty = (ippz - viewport->viewpoint.Pos.Z) * thread->Viewport->YaspectMul;
 		y1 = xs_RoundToInt(viewport->CenterY - (ty + psize) * yscale);
 		y2 = xs_RoundToInt(viewport->CenterY - (ty - psize) * yscale);
 
@@ -184,9 +192,9 @@ namespace swrenderer
 			map = GetColorTable(sector->Colormap, sector->SpecialColors[sector_t::sprites], true);
 		}
 
-		if (botpic != skyflatnum && particle->Pos.Z < botplane->ZatPoint(particle->Pos))
+		if (botpic != skyflatnum && ippz < botplane->ZatPoint(particle->Pos))
 			return;
-		if (toppic != skyflatnum && particle->Pos.Z >= topplane->ZatPoint(particle->Pos))
+		if (toppic != skyflatnum && ippz >= topplane->ZatPoint(particle->Pos))
 			return;
 
 		// store information in a vissprite
@@ -199,7 +207,7 @@ namespace swrenderer
 		//	vis->yscale *= InvZtoScale;
 		vis->depth = (float)tz;
 		vis->idepth = float(1 / tz);
-		vis->gpos = { (float)particle->Pos.X, (float)particle->Pos.Y, (float)particle->Pos.Z };
+		vis->gpos = { (float)ippx, (float)ippy, (float)ippz };
 		vis->y1 = y1;
 		vis->y2 = y2;
 		vis->x1 = x1;