now checks tangent vector crossproduct against surface normal to see if the tangents...

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4331 d7cf8633-e32d-0410-b094-e92efae38249

diff --git a/model_shared.c b/model_shared.c
index 369802d5a76536b3eff49993dddc6f97ab2d8039..1fe8aa3a0e6b2fc2bce968c38e075f637b269185 100644 (file)
--- a/model_shared.c
+++ b/model_shared.c
@@ -608,7 +608,7 @@ void Mod_ValidateElements(const int *elements, int numtriangles, int numverts, c
 
 void Mod_BuildBumpVectors(const float *v0, const float *v1, const float *v2, const float *tc0, const float *tc1, const float *tc2, float *svector3f, float *tvector3f, float *normal3f)
 {
-       float f;
+       float f, tangentcross[3];
        normal3f[0] = (v1[1] - v0[1]) * (v2[2] - v0[2]) - (v1[2] - v0[2]) * (v2[1] - v0[1]);
        normal3f[1] = (v1[2] - v0[2]) * (v2[0] - v0[0]) - (v1[0] - v0[0]) * (v2[2] - v0[2]);
        normal3f[2] = (v1[0] - v0[0]) * (v2[1] - v0[1]) - (v1[1] - v0[1]) * (v2[0] - v0[0]);
@@ -626,6 +626,13 @@ void Mod_BuildBumpVectors(const float *v0, const float *v1, const float *v2, con
        f = -DotProduct(svector3f, normal3f);
        VectorMA(svector3f, f, normal3f, svector3f);
        VectorNormalize(svector3f);
+       CrossProduct(svector3f, tvector3f, tangentcross);
+       // if texture is mapped the wrong way (counterclockwise), the tangents have to be flipped, this is detected by calculating a normal from the two tangents, and seeing if it is opposite the surface normal
+       if (DotProduct(tangentcross, normal3f) < 0)
+       {
+               VectorNegate(svector3f, svector3f);
+               VectorNegate(tvector3f, tvector3f);
+       }
 }
 
 // warning: this is an expensive function!