Fix T41406:

Disallow kernels bigger than 2x2 for blur/sharpen in projective painting
due to performance considerations.

release/scripts/startup/bl_ui/properties_paint_common.py

@@ -129,7 +129,8 @@ def brush_texpaint_common(panel, context, layout, brush, settings, projpaint=Fal
         col.row().prop(brush, "direction", expand=True)
         col.separator()
         col.prop(brush, "sharp_threshold")
-        col.prop(brush, "blur_kernel_radius")
+        if not projpaint:
+            col.prop(brush, "blur_kernel_radius")
         col.separator()
         col.prop(brush, "blur_mode")
     elif brush.image_tool == 'MASK':

source/blender/editors/sculpt_paint/paint_image.c

@@ -510,19 +510,32 @@ void imapaint_image_update(SpaceImage *sima, Image *image, ImBuf *ibuf, short te
 	}
 }
 
-/* paint blur kernels */
-BlurKernel *paint_new_blur_kernel(Brush *br)
+/* paint blur kernels. Projective painting enforces use of a 2x2 kernel due to lagging */
+BlurKernel *paint_new_blur_kernel(Brush *br, bool proj)
 {
 	int i, j;
 	BlurKernel *kernel = MEM_mallocN(sizeof(BlurKernel), "blur kernel");
-	int pixel_len = br->blur_kernel_radius;
+	float radius;
+	int side;
 	BlurKernelType type = br->blur_mode;
 
-	kernel->side = pixel_len * 2 + 1;
-	kernel->side_squared = kernel->side * kernel->side;
-	kernel->wdata = MEM_mallocN(sizeof(float) * kernel->side_squared, "blur kernel data");
-	kernel->pixel_len = pixel_len;
-
+	if (proj) {
+		radius = 0.5f;
+		
+		side = kernel->side = 2;
+		kernel->side_squared = kernel->side * kernel->side;
+		kernel->wdata = MEM_mallocN(sizeof(float) * kernel->side_squared, "blur kernel data");
+		kernel->pixel_len = radius;
+	}
+	else {
+		radius = br->blur_kernel_radius;
+		
+		side = kernel->side = radius * 2 + 1;
+		kernel->side_squared = kernel->side * kernel->side;
+		kernel->wdata = MEM_mallocN(sizeof(float) * kernel->side_squared, "blur kernel data");
+		kernel->pixel_len = br->blur_kernel_radius;
+	}
+	
 	switch (type) {
 		case KERNEL_BOX:
 			for (i = 0; i < kernel->side_squared; i++)
@@ -531,26 +544,19 @@ BlurKernel *paint_new_blur_kernel(Brush *br)
 
 		case KERNEL_GAUSSIAN:
 		{
-			float standard_dev = pixel_len / 3.0; /* at standard deviation of 3.0 kernel is at about zero */
-			int i_term = pixel_len + 1;
-
+			/* at standard deviation of 3.0 kernel is at about zero */			
+			float standard_dev = radius / 3.0f; 
+			
 			/* make the necessary adjustment to the value for use in the normal distribution formula */
 			standard_dev = standard_dev * standard_dev * 2;
 
-			kernel->wdata[pixel_len + pixel_len * kernel->side] = 1.0;
-			/* fill in all four quadrants at once */
-			for (i = 0; i < i_term; i++) {
-				for (j = 0; j < pixel_len; j++) {
-					float idist = pixel_len - i;
-					float jdist = pixel_len - j;
-
+			for (i = 0; i < side; i++) {
+				for (j = 0; j < side; j++) {
+					float idist = radius - i;
+					float jdist = radius - j;
 					float value = exp((idist * idist + jdist * jdist) / standard_dev);
-
-					kernel->wdata[i + j * kernel->side] =
-					kernel->wdata[(kernel->side - j - 1) + i * kernel->side] =
-					kernel->wdata[(kernel->side - i - 1) + (kernel->side - j - 1) * kernel->side] =
-					kernel->wdata[j + (kernel->side - i - 1) * kernel->side] =
-						value;
+					
+					kernel->wdata[i + j * side] = value;
 				}
 			}
 

source/blender/editors/sculpt_paint/paint_image_2d.c

@@ -1249,7 +1249,7 @@ void *paint_2d_new_stroke(bContext *C, wmOperator *op, int mode)
 	}
 
 	if (brush->imagepaint_tool == PAINT_TOOL_SOFTEN) {
-		s->blurkernel = paint_new_blur_kernel(brush);
+		s->blurkernel = paint_new_blur_kernel(brush, false);
 	}
 
 	paint_brush_init_tex(s->brush);

source/blender/editors/sculpt_paint/paint_image_proj.c

@@ -3763,7 +3763,7 @@ static void do_projectpaint_soften_f(ProjPaintState *ps, ProjPixel *projPixel, f
 	for (yk = 0; yk < kernel->side; yk++) {
 		for (xk = 0; xk < kernel->side; xk++) {
 			float rgba_tmp[4];
-			float co_ofs[2] = {xk - kernel->pixel_len, yk - kernel->pixel_len};
+			float co_ofs[2] = {2.0f * xk - 1.0f, 2.0f * yk - 1.0f};
 
 			add_v2_v2(co_ofs, projPixel->projCoSS);
 
@@ -3819,7 +3819,7 @@ static void do_projectpaint_soften(ProjPaintState *ps, ProjPixel *projPixel, flo
 	for (yk = 0; yk < kernel->side; yk++) {
 		for (xk = 0; xk < kernel->side; xk++) {
 			float rgba_tmp[4];
-			float co_ofs[2] = {xk - kernel->pixel_len, yk - kernel->pixel_len};
+			float co_ofs[2] = {2.0f * xk - 1.0f, 2.0f * yk - 1.0f};
 
 			add_v2_v2(co_ofs, projPixel->projCoSS);
 
@@ -4453,7 +4453,7 @@ static void project_state_init(bContext *C, Object *ob, ProjPaintState *ps, int
 			ps->mode = ((ps->mode == BRUSH_STROKE_INVERT) ^ ((brush->flag & BRUSH_DIR_IN) != 0) ?
 			            BRUSH_STROKE_INVERT : BRUSH_STROKE_NORMAL);
 
-			ps->blurkernel = paint_new_blur_kernel(brush);
+			ps->blurkernel = paint_new_blur_kernel(brush, true);
 		}
 
 		/* disable for 3d mapping also because painting on mirrored mesh can create "stripes" */

source/blender/editors/sculpt_paint/paint_intern.h

@@ -293,7 +293,7 @@ typedef struct {
 
 enum BlurKernelType;
 /* can be extended to other blur kernels later */
-BlurKernel *paint_new_blur_kernel(struct Brush *br);
+BlurKernel *paint_new_blur_kernel(struct Brush *br, bool proj);
 void paint_delete_blur_kernel(BlurKernel *);
 
 /* paint curve defines */