Fix T38529, Blur node size 0 doesn't work.

The blur operations were clamping the filter size to 1, which prevents
no-op blur nodes. Further any value < 1 would also be ignored and in
many combinations the filter scale setting ("Size") would only work in
integer steps.

Now most blur settings will work with smooth Size value scaling as well,
meaning you can choose a reasonably large filter size (e.g. 10) and then
use the Size factor to scale the actual blur radius smoothly.

Note that non-integer filter sizes also depend on the filter type
selected in the Blur node, e.g. "Flat" filtering will still ignore
smooth filter sizes. Gaussian filters work best for this purpose.

1 files changed, 23 insertions, 28 deletions

diff --git a/source/blender/compositor/operations/COM_GaussianAlphaYBlurOperation.cpp b/source/blender/compositor/operations/COM_GaussianAlphaYBlurOperation.cpp
index 4866fb9b428..fb407bf9ee4 100644
--- a/source/blender/compositor/operations/COM_GaussianAlphaYBlurOperation.cpp
+++ b/source/blender/compositor/operations/COM_GaussianAlphaYBlurOperation.cpp
@@ -32,7 +32,7 @@ extern "C" {
 GaussianAlphaYBlurOperation::GaussianAlphaYBlurOperation() : BlurBaseOperation(COM_DT_VALUE)
 {
 	this->m_gausstab = NULL;
-	this->m_rad = 0;
+	this->m_filtersize = 0;
 	this->m_falloff = -1;  /* intentionally invalid, so we can detect uninitialized values */
 }
 
@@ -54,12 +54,11 @@ void GaussianAlphaYBlurOperation::initExecution()
 	initMutex();
 
 	if (this->m_sizeavailable) {
-		float rad = this->m_size * this->m_data->sizey;
-		CLAMP(rad, 1.0f, MAX_GAUSSTAB_RADIUS);
-
-		this->m_rad = rad;
-		this->m_gausstab = BlurBaseOperation::make_gausstab(rad);
-		this->m_distbuf_inv = BlurBaseOperation::make_dist_fac_inverse(rad, this->m_falloff);
+		float rad = max_ff(m_size * m_data->sizey, 0.0f);
+		m_filtersize = min_ii(ceil(rad), MAX_GAUSSTAB_RADIUS);
+		
+		m_gausstab = BlurBaseOperation::make_gausstab(rad, m_filtersize);
+		m_distbuf_inv = BlurBaseOperation::make_dist_fac_inverse(rad, m_filtersize, m_falloff);
 	}
 }
 
@@ -67,20 +66,18 @@ void GaussianAlphaYBlurOperation::updateGauss()
 {
 	if (this->m_gausstab == NULL) {
 		updateSize();
-		float rad = this->m_size * this->m_data->sizey;
-		CLAMP(rad, 1.0f, MAX_GAUSSTAB_RADIUS);
-
-		this->m_rad = rad;
-		this->m_gausstab = BlurBaseOperation::make_gausstab(rad);
+		float rad = max_ff(m_size * m_data->sizey, 0.0f);
+		m_filtersize = min_ii(ceil(rad), MAX_GAUSSTAB_RADIUS);
+		
+		m_gausstab = BlurBaseOperation::make_gausstab(rad, m_filtersize);
 	}
 
 	if (this->m_distbuf_inv == NULL) {
 		updateSize();
-		float rad = this->m_size * this->m_data->sizex;
-		CLAMP(rad, 1.0f, MAX_GAUSSTAB_RADIUS);
-
-		this->m_rad = rad;
-		this->m_distbuf_inv = BlurBaseOperation::make_dist_fac_inverse(rad, this->m_falloff);
+		float rad = max_ff(m_size * m_data->sizey, 0.0f);
+		m_filtersize = min_ii(ceil(rad), MAX_GAUSSTAB_RADIUS);
+		
+		m_distbuf_inv = BlurBaseOperation::make_dist_fac_inverse(rad, m_filtersize, m_falloff);
 	}
 }
 
@@ -98,12 +95,10 @@ void GaussianAlphaYBlurOperation::executePixel(float output[4], int x, int y, vo
 	int bufferstartx = inputBuffer->getRect()->xmin;
 	int bufferstarty = inputBuffer->getRect()->ymin;
 
-	int miny = y - this->m_rad;
-	int maxy = y + this->m_rad;
-	int minx = x;
-	miny = max(miny, inputBuffer->getRect()->ymin);
-	minx = max(minx, inputBuffer->getRect()->xmin);
-	maxy = min(maxy, inputBuffer->getRect()->ymax - 1);
+	rcti &rect = *inputBuffer->getRect();
+	int xmin = max_ii(x,                    rect.xmin);
+	int ymin = max_ii(y - m_filtersize,     rect.ymin);
+	int ymax = min_ii(y + m_filtersize + 1, rect.ymax);
 
 	/* *** this is the main part which is different to 'GaussianYBlurOperation'  *** */
 	int step = getStep();
@@ -116,10 +111,10 @@ void GaussianAlphaYBlurOperation::executePixel(float output[4], int x, int y, vo
 	float value_max = finv_test(buffer[(x * 4) + (y * 4 * bufferwidth)], do_invert); /* init with the current color to avoid unneeded lookups */
 	float distfacinv_max = 1.0f; /* 0 to 1 */
 
-	for (int ny = miny; ny <= maxy; ny += step) {
-		int bufferindex = ((minx - bufferstartx) * 4) + ((ny - bufferstarty) * 4 * bufferwidth);
+	for (int ny = ymin; ny < ymax; ny += step) {
+		int bufferindex = ((xmin - bufferstartx) * 4) + ((ny - bufferstarty) * 4 * bufferwidth);
 
-		const int index = (ny - y) + this->m_rad;
+		const int index = (ny - y) + this->m_filtersize;
 		float value = finv_test(buffer[bufferindex], do_invert);
 		float multiplier;
 
@@ -179,8 +174,8 @@ bool GaussianAlphaYBlurOperation::determineDependingAreaOfInterest(rcti *input,
 		if (this->m_sizeavailable && this->m_gausstab != NULL) {
 			newInput.xmax = input->xmax;
 			newInput.xmin = input->xmin;
-			newInput.ymax = input->ymax + this->m_rad + 1;
-			newInput.ymin = input->ymin - this->m_rad - 1;
+			newInput.ymax = input->ymax + this->m_filtersize + 1;
+			newInput.ymin = input->ymin - this->m_filtersize - 1;
 		}
 		else {
 			newInput.xmax = this->getWidth();