From: havoc <havoc@d7cf8633-e32d-0410-b094-e92efae38249>
Date: Tue, 17 Sep 2013 01:17:53 +0000 (+0000)
Subject: reworked tcmod to wrap shadertime every 9.1 hours (32768 seconds) rather
X-Git-Tag: xonotic-v0.8.0~133
X-Git-Url: https://git.rm.cloudns.org/?a=commitdiff_plain;h=77bce10e745c4bd70904b3f52e76cf6314a003ae;p=xonotic%2Fdarkplaces.git

reworked tcmod to wrap shadertime every 9.1 hours (32768 seconds) rather
than attempting to fixup precision issues in tcmod scroll, which was
breaking shaders that had other tcmod effects after tcmod scroll (or if
they used clampmap)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12004 d7cf8633-e32d-0410-b094-e92efae38249
::stable-branch::merge=5927c6f5fe5fd0fcd20072ce6679d9e1c7b4212e
---

diff --git a/gl_rmain.c b/gl_rmain.c
index 8f69fb09..76931c35 100644
--- a/gl_rmain.c
+++ b/gl_rmain.c
@@ -8001,10 +8001,21 @@ static float R_EvaluateQ3WaveFunc(q3wavefunc_t func, const float *parms)
 static void R_tcMod_ApplyToMatrix(matrix4x4_t *texmatrix, q3shaderinfo_layer_tcmod_t *tcmod, int currentmaterialflags)
 {
 	int w, h, idx;
-	double f;
-	double offsetd[2];
+	float shadertime;
+	float f;
 	float tcmat[12];
 	matrix4x4_t matrix, temp;
+	// if shadertime exceeds about 9 hours (32768 seconds), just wrap it,
+	// it's better to have one huge fixup every 9 hours than gradual
+	// degradation over time which looks consistently bad after many hours.
+	//
+	// tcmod scroll in particular suffers from this degradation which can't be
+	// effectively worked around even with floor() tricks because we don't
+	// know if tcmod scroll is the last tcmod being applied, and for clampmap
+	// a workaround involving floor() would be incorrect anyway...
+	shadertime = rsurface.shadertime;
+	if (shadertime >= 32768.0f)
+		shadertime -= floor(rsurface.shadertime * (1.0f / 32768.0f)) * 32768.0f;
 	switch(tcmod->tcmod)
 	{
 		case Q3TCMOD_COUNT:
@@ -8020,19 +8031,18 @@ static void R_tcMod_ApplyToMatrix(matrix4x4_t *texmatrix, q3shaderinfo_layer_tcm
 			Matrix4x4_CreateTranslate(&matrix, 0, 0, 0);
 			break;
 		case Q3TCMOD_ROTATE:
-			f = tcmod->parms[0] * rsurface.shadertime;
 			Matrix4x4_CreateTranslate(&matrix, 0.5, 0.5, 0);
-			Matrix4x4_ConcatRotate(&matrix, (f / 360 - floor(f / 360)) * 360, 0, 0, 1);
+			Matrix4x4_ConcatRotate(&matrix, tcmod->parms[0] * rsurface.shadertime, 0, 0, 1);
 			Matrix4x4_ConcatTranslate(&matrix, -0.5, -0.5, 0);
 			break;
 		case Q3TCMOD_SCALE:
 			Matrix4x4_CreateScale3(&matrix, tcmod->parms[0], tcmod->parms[1], 1);
 			break;
 		case Q3TCMOD_SCROLL:
-			// extra care is needed because of precision breakdown with large values of time
-			offsetd[0] = tcmod->parms[0] * rsurface.shadertime;
-			offsetd[1] = tcmod->parms[1] * rsurface.shadertime;
-			Matrix4x4_CreateTranslate(&matrix, offsetd[0] - floor(offsetd[0]), offsetd[1] - floor(offsetd[1]), 0);
+			// this particular tcmod is the most prone to precision breakdown
+			// at large values, but as we wrap shadertime it won't be obvious
+			// in practice.
+			Matrix4x4_CreateTranslate(&matrix, tcmod->parms[0] * rsurface.shadertime, tcmod->parms[1] * rsurface.shadertime, 0);
 			break;
 		case Q3TCMOD_PAGE: // poor man's animmap (to store animations into a single file, useful for HTTP downloaded textures)
 			w = (int) tcmod->parms[0];