compositor - EWA filter was blurring too much by default, this caused the displace node to blur the image when no displacement was applied, making images fuzzy, the original C code has an interpolation option.

Added this option back and use for displace and UV composite nodes.

source/blender/compositor/intern/COM_MemoryBuffer.cpp

@@ -259,7 +259,10 @@ float clipuv(float x, float limit)
 	return x;
 }
 
-void MemoryBuffer::readEWA(float result[4], float fx, float fy, float dx, float dy)
+/**
+ * \note \a sampler at the moment is either 'COM_PS_NEAREST' or not, other values won't matter.
+ */
+void MemoryBuffer::readEWA(float result[4], float fx, float fy, float dx, float dy, PixelSampler sampler)
 {
 	const int width = this->getWidth(), height = this->getHeight();
 	
@@ -280,7 +283,7 @@ void MemoryBuffer::readEWA(float result[4], float fx, float fy, float dx, float
 	// Use a different radius based on interpolation switch, just enough to anti-alias when interpolation is off,
 	// and slightly larger to make result a bit smoother than bilinear interpolation when interpolation is on
 	// (minimum values: const float rmin = intpol ? 1.f : 0.5f;)
-	const float rmin = 1.5625f / ff2;
+	const float rmin = ((sampler != COM_PS_NEAREST) ? 1.5625f : 0.765625f) / ff2;
 	imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
 	if ((b2 = b * b) < rmin) {
 		if ((a2 = a * a) < rmin) {

source/blender/compositor/intern/COM_MemoryBuffer.h

@@ -202,7 +202,7 @@ public:
 		
 
 
-	void readEWA(float result[4], float fx, float fy, float dx, float dy);
+	void readEWA(float result[4], float fx, float fy, float dx, float dy, PixelSampler sampler);
 	
 	/**
 	 * @brief is this MemoryBuffer a temporarily buffer (based on an area, not on a chunk)

source/blender/compositor/intern/COM_SocketReader.h

@@ -88,7 +88,7 @@ protected:
 	 * @param dy
 	 * @param inputBuffers chunks that can be read by their ReadBufferOperation.
 	 */
-	virtual void executePixel(float output[4], float x, float y, float dx, float dy) {}
+	virtual void executePixel(float output[4], float x, float y, float dx, float dy, PixelSampler sampler) {}
 
 public:
 	inline void read(float *result, float x, float y, PixelSampler sampler) {
@@ -97,8 +97,8 @@ public:
 	inline void read(float *result, int x, int y, void *chunkData) {
 		executePixel(result, x, y, chunkData);
 	}
-	inline void read(float *result, float x, float y, float dx, float dy) {
-		executePixel(result, x, y, dx, dy);
+	inline void read(float *result, float x, float y, float dx, float dy, PixelSampler sampler) {
+		executePixel(result, x, y, dx, dy, sampler);
 	}
 
 	virtual void *initializeTileData(rcti *rect) { return 0; }

source/blender/compositor/operations/COM_DisplaceOperation.cpp

@@ -95,8 +95,8 @@ void DisplaceOperation::executePixel(float output[4], int x, int y, void *data)
 	dxt = signf(dxt) * maxf(fabsf(dxt), DISPLACE_EPSILON) / this->getWidth();
 	dyt = signf(dyt) * maxf(fabsf(dyt), DISPLACE_EPSILON) / this->getHeight();
 
-	/* EWA filtering */
-	this->m_inputColorProgram->read(output, u, v, dxt, dyt);
+	/* EWA filtering (without nearest it gets blurry with NO distortion) */
+	this->m_inputColorProgram->read(output, u, v, dxt, dyt, COM_PS_NEAREST);
 }
 
 void DisplaceOperation::deinitExecution()

source/blender/compositor/operations/COM_MapUVOperation.cpp

@@ -107,7 +107,7 @@ void MapUVOperation::executePixel(float output[4], float x, float y, PixelSample
 	u = inputUV[0] * this->m_inputColorProgram->getWidth();
 	v = inputUV[1] * this->m_inputColorProgram->getHeight();
 
-	this->m_inputColorProgram->read(output, u, v, dx, dy);
+	this->m_inputColorProgram->read(output, u, v, dx, dy, COM_PS_NEAREST);
 
 	/* "premul" */
 	if (alpha < 1.0f) {

source/blender/compositor/operations/COM_ReadBufferOperation.cpp

@@ -59,9 +59,9 @@ void ReadBufferOperation::executePixel(float output[4], float x, float y, PixelS
 	}
 }
 
-void ReadBufferOperation::executePixel(float output[4], float x, float y, float dx, float dy)
+void ReadBufferOperation::executePixel(float output[4], float x, float y, float dx, float dy, PixelSampler sampler)
 {
-	m_buffer->readEWA(output, x, y, dx, dy);
+	m_buffer->readEWA(output, x, y, dx, dy, sampler);
 }
 
 bool ReadBufferOperation::determineDependingAreaOfInterest(rcti *input, ReadBufferOperation *readOperation, rcti *output)

source/blender/compositor/operations/COM_ReadBufferOperation.h

@@ -40,7 +40,7 @@ public:
 	
 	void *initializeTileData(rcti *rect);
 	void executePixel(float output[4], float x, float y, PixelSampler sampler);
-	void executePixel(float output[4], float x, float y, float dx, float dy);
+	void executePixel(float output[4], float x, float y, float dx, float dy, PixelSampler sampler);
 	const bool isReadBufferOperation() const { return true; }
 	void setOffset(unsigned int offset) { this->m_offset = offset; }
 	unsigned int getOffset() { return this->m_offset; }