Fix ##30455: Orthographic grid alignment jumps/shifts when zooming

Issue was caused by precision errors with floats.
Made internal grid drawing stuff using doubles and also added some
functions to multiply double vector by float matrix which also makes
all intermediate calculation in doubles.

1 files changed, 15 insertions, 18 deletions

diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index 3a3d5a6683f..a9533b57d8f 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -225,21 +225,21 @@ int ED_view3d_clipping_test(RegionView3D *rv3d, const float vec[3], const int is
 /* ********* end custom clipping *********** */
 
 
-static void drawgrid_draw(ARegion *ar, float wx, float wy, float x, float y, float dx)
+static void drawgrid_draw(ARegion *ar, double wx, double wy, double x, double y, double dx)
 {	
-	float verts[2][2];
+	double verts[2][2];
 
 	x+= (wx); 
 	y+= (wy);
 
 	/* set fixed 'Y' */
 	verts[0][1]= 0.0f;
-	verts[1][1]= (float)ar->winy;
+	verts[1][1]= (double)ar->winy;
 
 	/* iter over 'X' */
-	verts[0][0] = verts[1][0] = x-dx*floorf(x/dx);
+	verts[0][0] = verts[1][0] = x-dx*floor(x/dx);
 	glEnableClientState(GL_VERTEX_ARRAY);
-	glVertexPointer(2, GL_FLOAT, 0, verts);
+	glVertexPointer(2, GL_DOUBLE, 0, verts);
 
 	while (verts[0][0] < ar->winx) {
 		glDrawArrays(GL_LINES, 0, 2);
@@ -248,10 +248,10 @@ static void drawgrid_draw(ARegion *ar, float wx, float wy, float x, float y, flo
 
 	/* set fixed 'X' */
 	verts[0][0]= 0.0f;
-	verts[1][0]= (float)ar->winx;
+	verts[1][0]= (double)ar->winx;
 
 	/* iter over 'Y' */
-	verts[0][1]= verts[1][1]= y-dx*floorf(y/dx);
+	verts[0][1]= verts[1][1]= y-dx*floor(y/dx);
 	while (verts[0][1] < ar->winy) {
 		glDrawArrays(GL_LINES, 0, 2);
 		verts[0][1] = verts[1][1] = verts[0][1] + dx;
@@ -266,16 +266,13 @@ static void drawgrid(UnitSettings *unit, ARegion *ar, View3D *v3d, const char **
 {
 	/* extern short bgpicmode; */
 	RegionView3D *rv3d= ar->regiondata;
-	float wx, wy, x, y, fw, fx, fy, dx;
-	float vec4[4];
+	double wx, wy, x, y, fw, fx, fy, dx;
+	double vec4[4];
 	unsigned char col[3], col2[3];
 
-	vec4[0]=vec4[1]=vec4[2]=0.0; 
-	vec4[3]= 1.0;
-	mul_m4_v4(rv3d->persmat, vec4);
-	fx= vec4[0]; 
-	fy= vec4[1]; 
-	fw= vec4[3];
+	fx= rv3d->persmat[3][0];
+	fy= rv3d->persmat[3][1];
+	fw= rv3d->persmat[3][3];
 
 	wx= (ar->winx/2.0);	/* because of rounding errors, grid at wrong location */
 	wy= (ar->winy/2.0);
@@ -287,7 +284,7 @@ static void drawgrid(UnitSettings *unit, ARegion *ar, View3D *v3d, const char **
 
 	vec4[2]= 0.0;
 	vec4[3]= 1.0;
-	mul_m4_v4(rv3d->persmat, vec4);
+	mul_m4_v4d(rv3d->persmat, vec4);
 	fx= vec4[0]; 
 	fy= vec4[1]; 
 	fw= vec4[3];
@@ -305,7 +302,7 @@ static void drawgrid(UnitSettings *unit, ARegion *ar, View3D *v3d, const char **
 		 * items are less useful when dealing with units */
 		void *usys;
 		int len, i;
-		float dx_scalar;
+		double dx_scalar;
 		float blend_fac;
 
 		bUnit_GetSystem(&usys, &len, unit->system, B_UNIT_LENGTH);
@@ -313,7 +310,7 @@ static void drawgrid(UnitSettings *unit, ARegion *ar, View3D *v3d, const char **
 		if (usys) {
 			i= len;
 			while (i--) {
-				float scalar= bUnit_GetScaler(usys, i);
+				double scalar= bUnit_GetScaler(usys, i);
 
 				dx_scalar = dx * scalar / unit->scale_length;
 				if (dx_scalar < (GRID_MIN_PX*2))