Fix dancing sprites regression

src/rendering/swrenderer/line/r_wallsetup.cpp

@@ -54,6 +54,8 @@ namespace swrenderer
 		auto viewport = thread->Viewport.get();
 		RenderPortal* renderportal = thread->Portal.get();
 
+		// Rotate to view direction:
+
 		tleft.X = float(pt1.X * viewport->viewpoint.Sin - pt1.Y * viewport->viewpoint.Cos);
 		tright.X = float(pt2.X * viewport->viewpoint.Sin - pt2.Y * viewport->viewpoint.Cos);
 
@@ -68,6 +70,8 @@ namespace swrenderer
 			std::swap(tleft.Y, tright.Y);
 		}
 
+		// Edge clip:
+
 		float fsx1, fsz1, fsx2, fsz2;
 
 		if (tleft.X >= -tleft.Y)
@@ -112,23 +116,20 @@ namespace swrenderer
 		if (fsz2 < TOO_CLOSE_Z)
 			return true;
 
+		// Find screen range covered by the line:
+
 		sx1 = xs_RoundToInt(fsx1);
 		sx2 = xs_RoundToInt(fsx2);
 
-		float delta = fsx2 - fsx1;
-		float t1 = (sx1 + 0.5f - fsx1) / delta;
-		float t2 = (sx2 + 0.5f - fsx1) / delta;
-		float invZ1 = 1.0f / fsz1;
-		float invZ2 = 1.0f / fsz2;
-		sz1 = 1.0f / (invZ1 * (1.0f - t1) + invZ2 * t1);
-		sz2 = 1.0f / (invZ1 * (1.0f - t2) + invZ2 * t2);
-
 		if (sx2 <= sx1)
 			return true;
 
+		// Remap texture coordinates to the part covered by the line segment:
+
 		if (lineseg && lineseg->linedef)
 		{
 			line_t* line = lineseg->linedef;
+			float t1, t2;
 			if (fabs(line->delta.X) > fabs(line->delta.Y))
 			{
 				t1 = (lineseg->v1->fX() - line->v1->fX()) / line->delta.X;
@@ -150,6 +151,23 @@ namespace swrenderer
 			tx2 = t1 + tx2 * (t2 - t1);
 		}
 
+		// Calculate screen depths for the start and end points (resulting values are at the pixel center):
+
+		float delta = fsx2 - fsx1;
+		float t1 = (sx1 + 0.5f - fsx1) / delta;
+		float t2 = (sx2 + 0.5f - fsx1) / delta;
+		float invZ1 = 1.0f / fsz1;
+		float invZ2 = 1.0f / fsz2;
+		sz1 = 1.0f / (invZ1 * (1.0f - t1) + invZ2 * t1);
+		sz2 = 1.0f / (invZ1 * (1.0f - t2) + invZ2 * t2);
+
+		// Adjust texture coordinates to also be at the pixel centers:
+
+		float ftx1 = tx1 * invZ1;
+		float ftx2 = tx2 * invZ2;
+		tx1 = (ftx1 * (1.0f - t1) + ftx2 * t1) * sz1;
+		tx2 = (ftx1 * (1.0f - t2) + ftx2 * t2) * sz2;
+
 		return false;
 	}
 

src/rendering/swrenderer/viewport/r_spritedrawer.cpp

@@ -70,9 +70,6 @@ namespace swrenderer
 			iscale = -iscale;
 		float vstepY = iscale / WallC.sz1 / (viewport->InvZtoScale / WallC.sz1);
 
-		wpos += wstepX * 0.5f;
-		upos += ustepX * 0.5f;
-
 		int x1 = MAX<int>(WallC.sx1, clipx1);
 		int x2 = MIN<int>(WallC.sx2, clipx2);
 		if (x1 >= x2)
@@ -165,7 +162,7 @@ namespace swrenderer
 		}
 	}
 
-	void SpriteDrawerArgs::DrawMaskedColumn(RenderThread* thread, int x, int y1, int cliptop, int clipbottom, uint32_t texelX, uint32_t texelStepX, uint32_t texelStepY, float scaleV, bool flipY, FSoftwareTexture* tex, int texwidth, int texheight, bool bgra, FRenderStyle style)
+	void SpriteDrawerArgs::DrawMaskedColumn(RenderThread* thread, int x, float y1, int cliptop, int clipbottom, uint32_t texelX, uint32_t texelStepX, uint32_t texelStepY, float scaleV, bool flipY, FSoftwareTexture* tex, int texwidth, int texheight, bool bgra, FRenderStyle style)
 	{
 		const FSoftwareTextureSpan* span;
 		if (bgra)
@@ -230,8 +227,8 @@ namespace swrenderer
 				const int top = span->TopOffset;
 
 				// calculate unclipped screen coordinates for post
-				dc_yl = (int)(y1 + top / scaleV + 0.5f);
+				dc_yl = xs_RoundToInt(y1 + top / scaleV);
-				dc_yh = (int)(y1 + (top + length) / scaleV + 0.5f);
+				dc_yh = xs_RoundToInt(y1 + (top + length) / scaleV);
 
 				if (flipY)
 					std::swap(dc_yl, dc_yh);
@@ -268,8 +265,8 @@ namespace swrenderer
 				const int top = span->TopOffset;
 
 				// calculate unclipped screen coordinates for post
-				dc_yl = (int)(y1 + top / scaleV + 0.5f);
+				dc_yl = xs_RoundToInt(y1 + top / scaleV);
-				dc_yh = (int)(y1 + (top + length) / scaleV + 0.5f);
+				dc_yh = xs_RoundToInt(y1 + (top + length) / scaleV);
 
 				if (flipY)
 					std::swap(dc_yl, dc_yh);

src/rendering/swrenderer/viewport/r_spritedrawer.h

@@ -69,7 +69,7 @@ namespace swrenderer
 		RenderViewport *Viewport() const { return dc_viewport; }
 
 	private:
-		void DrawMaskedColumn(RenderThread* thread, int x, int y1, int cliptop, int clipbottom, uint32_t texelX, uint32_t texelStepX, uint32_t texelStepY, float scaleV, bool flipY, FSoftwareTexture* tex, int texwidth, int texheight, bool bgra, FRenderStyle style);
+		void DrawMaskedColumn(RenderThread* thread, int x, float y1, int cliptop, int clipbottom, uint32_t texelX, uint32_t texelStepX, uint32_t texelStepY, float scaleV, bool flipY, FSoftwareTexture* tex, int texwidth, int texheight, bool bgra, FRenderStyle style);
 
 		void SetDest(RenderViewport* viewport, int x, int y);
 		void SetCount(int count) { dc_count = count; }