Add a nearest neighbour sampling mode to the compositor MapUV node.

By default the MapUV node does anisotropic filtering, but this interferes
with some (NPR) workflows, for example when you generate to UV coordinates
to use a separate image as a LUT, or for pixel based distortions.

@@ -19,6 +19,7 @@ void MapUVNode::convert_to_operations(NodeConverter &converter,
 
   MapUVOperation *operation = new MapUVOperation();
   operation->set_alpha(float(node->custom1));
+  operation->set_nearestNeighbour(bool(node->custom2));

@@ -70,3 +60,1 @@
-                                     dv / input_color_program_->get_height());
-  if (factor < 0.0f) {
-    alpha = 0.0f;
+  if (nearest_neighbour_) {

@@ -13,2 +13,4 @@
     .compute_source("compositor_map_uv.glsl")
     .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_map_uv_nearest_neighbour)

@@ -6924,2 +6924,4 @@
   RNA_def_property_ui_text(prop, "Alpha", "");
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+  prop = RNA_def_property(srna, "nearest_neighbour", PROP_BOOLEAN, PROP_NONE);

@@ -54,0 +55,4 @@
+    bool nearest_neighbour = get_nearest_neighbour();
+
+    GPUShader *shader = nearest_neighbour ?
+                            context().get_shader("compositor_map_uv_nearest_neighbour") :

@@ -90,0 +97,4 @@
+
+  bool get_nearest_neighbour()
+  {
+    return bnode().custom2 != 0;

@@ -19,6 +19,8 @@ void MapUVNode::convert_to_operations(NodeConverter &converter,
 
   MapUVOperation *operation = new MapUVOperation();
   operation->set_alpha(float(node->custom1));
+  operation->set_nearestNeighbour(static_cast<CMPNodeMapUVFiltering>(node->custom2) ==

@@ -2539,6 +2539,12 @@ typedef enum CMPNodeCombSepColorMode {
   CMP_NODE_COMBSEP_COLOR_YUV = 4,
 } CMPNodeCombSepColorMode;
 
+/* Filtering modes Compositor MapUV node */

@@ -2542,0 +2542,4 @@
+/* Filtering modes Compositor MapUV node */
+typedef enum CMPNodeMapUVFiltering {
+  CMP_NODE_MAPUV_ANISOTROPIC = 0,
+  CMP_NODE_MAPUV_NEARESTNEIGHBOUR = 1,

@@ -0,0 +10,4 @@
+
+  vec2 uv_coordinates = texture_load(uv_tx, texel).xy;
+
+  /* Sample the input using the UV coordinates passing in the computed gradients in order to

@@ -37,6 +37,7 @@ static void cmp_node_map_uv_declare(NodeDeclarationBuilder &b)
 static void node_composit_buts_map_uv(uiLayout *layout, bContext * /*C*/, PointerRNA *ptr)
 {
   uiItemR(layout, ptr, "alpha", UI_ITEM_R_SPLIT_EMPTY_NAME, nullptr, ICON_NONE);
+  uiItemR(layout, ptr, "filter_type", UI_ITEM_R_SPLIT_EMPTY_NAME, nullptr, ICON_NONE);

@@ -60,3 +64,4 @@
+    }
 
     const Result &input_image = get_input("Image");
     GPU_texture_mipmap_mode(input_image.texture(), true, true);

@@ -90,0 +98,4 @@
+    return bnode().custom2 == CMP_NODE_MAP_UV_FILTERING_NEAREST;
+  }
+
+ private: