Create shadow_vec for altering shadow computation

In 2.1 and 3.0, light_vec could be modified for altering shadow_computations.
But it broke shadows when rotating light. shadow_vec would do the same, but without breaking
shadows in rotated lights if not used.

Add inverse light transformation to shadow vec, so it's not affected when rotating lights;

Added usage define for shadow vec.

For shadow vec working properly when rotating a light, it's needed to multiply it by light_matrix normalized. Added usage define in order to don't do that if shadow_vec not used.

4 files changed, 39 insertions, 17 deletions

diff --git a/drivers/gles2/shader_compiler_gles2.cpp b/drivers/gles2/shader_compiler_gles2.cpp
index 25bab0e97a..b7b76b510d 100644
--- a/drivers/gles2/shader_compiler_gles2.cpp
+++ b/drivers/gles2/shader_compiler_gles2.cpp
@@ -920,6 +920,7 @@ ShaderCompilerGLES2::ShaderCompilerGLES2() {
 	actions[VS::SHADER_CANVAS_ITEM].renames["LIGHT_UV"] = "light_uv";
 	actions[VS::SHADER_CANVAS_ITEM].renames["LIGHT"] = "light";
 	actions[VS::SHADER_CANVAS_ITEM].renames["SHADOW_COLOR"] = "shadow_color";
+	actions[VS::SHADER_CANVAS_ITEM].renames["SHADOW_VEC"] = "shadow_vec";
 
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["COLOR"] = "#define COLOR_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["SCREEN_TEXTURE"] = "#define SCREEN_TEXTURE_USED\n";
@@ -929,6 +930,7 @@ ShaderCompilerGLES2::ShaderCompilerGLES2() {
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["NORMALMAP"] = "#define NORMALMAP_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["LIGHT"] = "#define USE_LIGHT_SHADER_CODE\n";
 	actions[VS::SHADER_CANVAS_ITEM].render_mode_defines["skip_vertex_transform"] = "#define SKIP_TRANSFORM_USED\n";
+	actions[VS::SHADER_CANVAS_ITEM].usage_defines["SHADOW_VEC"] = "#define SHADOW_VEC_USED\n";
 
 	// Ported from GLES3
 
diff --git a/drivers/gles2/shaders/canvas.glsl b/drivers/gles2/shaders/canvas.glsl
index fa0b315e29..08548ded17 100644
--- a/drivers/gles2/shaders/canvas.glsl
+++ b/drivers/gles2/shaders/canvas.glsl
@@ -331,6 +331,7 @@ void light_compute(
 		inout vec4 light_color,
 		vec2 light_uv,
 		inout vec4 shadow_color,
+		inout vec2 shadow_vec,
 		vec3 normal,
 		vec2 uv,
 #if defined(SCREEN_UV_USED)
@@ -407,6 +408,7 @@ FRAGMENT_SHADER_CODE
 #ifdef USE_LIGHTING
 
 	vec2 light_vec = transformed_light_uv;
+	vec2 shadow_vec = transformed_light_uv;
 
 	if (normal_used) {
 		normal.xy = mat2(local_rot.xy, local_rot.zw) * normal.xy;
@@ -434,6 +436,7 @@ FRAGMENT_SHADER_CODE
 				real_light_color,
 				light_uv,
 				real_light_shadow_color,
+				shadow_vec,
 				normal,
 				uv,
 #if defined(SCREEN_UV_USED)
@@ -452,11 +455,18 @@ FRAGMENT_SHADER_CODE
 		color *= light;
 
 #ifdef USE_SHADOWS
-		// Reset light_vec to compute shadows, the shadow map is created from the light origin, so it only
-		// makes sense to compute shadows from there.
-		light_vec = light_uv_interp.zw;
 
-		float angle_to_light = -atan(light_vec.x, light_vec.y);
+#ifdef SHADOW_VEC_USED
+		mat3 inverse_light_matrix = mat3(light_matrix);
+		inverse_light_matrix[0] = normalize(inverse_light_matrix[0]);
+		inverse_light_matrix[1] = normalize(inverse_light_matrix[1]);
+		inverse_light_matrix[2] = normalize(inverse_light_matrix[2]);
+		shadow_vec = (inverse_light_matrix * vec3(shadow_vec, 0.0)).xy;
+#else
+		shadow_vec = light_uv_interp.zw;
+#endif
+
+		float angle_to_light = -atan(shadow_vec.x, shadow_vec.y);
 		float PI = 3.14159265358979323846264;
 		/*int i = int(mod(floor((angle_to_light+7.0*PI/6.0)/(4.0*PI/6.0))+1.0, 3.0)); // +1 pq os indices estao em ordem 2,0,1 nos arrays
 		float ang*/
@@ -467,18 +477,18 @@ FRAGMENT_SHADER_CODE
 		vec2 point;
 		float sh;
 		if (abs_angle < 45.0 * PI / 180.0) {
-			point = light_vec;
+			point = shadow_vec;
 			sh = 0.0 + (1.0 / 8.0);
 		} else if (abs_angle > 135.0 * PI / 180.0) {
-			point = -light_vec;
+			point = -shadow_vec;
 			sh = 0.5 + (1.0 / 8.0);
 		} else if (angle_to_light > 0.0) {
 
-			point = vec2(light_vec.y, -light_vec.x);
+			point = vec2(shadow_vec.y, -shadow_vec.x);
 			sh = 0.25 + (1.0 / 8.0);
 		} else {
 
-			point = vec2(-light_vec.y, light_vec.x);
+			point = vec2(-shadow_vec.y, shadow_vec.x);
 			sh = 0.75 + (1.0 / 8.0);
 		}
 
diff --git a/drivers/gles3/shader_compiler_gles3.cpp b/drivers/gles3/shader_compiler_gles3.cpp
index f826bdf5a2..f1ca3a8549 100644
--- a/drivers/gles3/shader_compiler_gles3.cpp
+++ b/drivers/gles3/shader_compiler_gles3.cpp
@@ -910,6 +910,7 @@ ShaderCompilerGLES3::ShaderCompilerGLES3() {
 	actions[VS::SHADER_CANVAS_ITEM].renames["LIGHT_UV"] = "light_uv";
 	actions[VS::SHADER_CANVAS_ITEM].renames["LIGHT"] = "light";
 	actions[VS::SHADER_CANVAS_ITEM].renames["SHADOW_COLOR"] = "shadow_color";
+	actions[VS::SHADER_CANVAS_ITEM].renames["SHADOW_VEC"] = "shadow_vec";
 
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["COLOR"] = "#define COLOR_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["SCREEN_TEXTURE"] = "#define SCREEN_TEXTURE_USED\n";
@@ -918,6 +919,7 @@ ShaderCompilerGLES3::ShaderCompilerGLES3() {
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["NORMAL"] = "#define NORMAL_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["NORMALMAP"] = "#define NORMALMAP_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].usage_defines["LIGHT"] = "#define USE_LIGHT_SHADER_CODE\n";
+	actions[VS::SHADER_CANVAS_ITEM].usage_defines["SHADOW_VEC"] = "#define SHADOW_VEC_USED\n";
 	actions[VS::SHADER_CANVAS_ITEM].render_mode_defines["skip_vertex_transform"] = "#define SKIP_TRANSFORM_USED\n";
 
 	/** SPATIAL SHADER **/
diff --git a/drivers/gles3/shaders/canvas.glsl b/drivers/gles3/shaders/canvas.glsl
index 10c8764b8e..e83f53d648 100644
--- a/drivers/gles3/shaders/canvas.glsl
+++ b/drivers/gles3/shaders/canvas.glsl
@@ -345,6 +345,7 @@ void light_compute(
 		inout vec4 light_color,
 		vec2 light_uv,
 		inout vec4 shadow_color,
+		inout vec2 shadow_vec,
 		vec3 normal,
 		vec2 uv,
 #if defined(SCREEN_UV_USED)
@@ -512,6 +513,7 @@ FRAGMENT_SHADER_CODE
 #ifdef USE_LIGHTING
 
 	vec2 light_vec = transformed_light_uv;
+	vec2 shadow_vec = transformed_light_uv;
 
 	if (normal_used) {
 		normal.xy = mat2(local_rot.xy, local_rot.zw) * normal.xy;
@@ -539,6 +541,7 @@ FRAGMENT_SHADER_CODE
 				real_light_color,
 				light_uv,
 				real_light_shadow_color,
+				shadow_vec,
 				normal,
 				uv,
 #if defined(SCREEN_UV_USED)
@@ -557,11 +560,16 @@ FRAGMENT_SHADER_CODE
 		color *= light;
 
 #ifdef USE_SHADOWS
-		// Reset light_vec to compute shadows, the shadow map is created from the light origin, so it only
-		// makes sense to compute shadows from there.
-		light_vec = light_uv_interp.zw;
-
-		float angle_to_light = -atan(light_vec.x, light_vec.y);
+#ifdef SHADOW_VEC_USED
+		mat3 inverse_light_matrix = mat3(light_matrix);
+		inverse_light_matrix[0] = normalize(inverse_light_matrix[0]);
+		inverse_light_matrix[1] = normalize(inverse_light_matrix[1]);
+		inverse_light_matrix[2] = normalize(inverse_light_matrix[2]);
+		shadow_vec = (mat3(inverse_light_matrix) * vec3(shadow_vec, 0.0)).xy;
+#else
+		shadow_vec = light_uv_interp.zw;
+#endif
+		float angle_to_light = -atan(shadow_vec.x, shadow_vec.y);
 		float PI = 3.14159265358979323846264;
 		/*int i = int(mod(floor((angle_to_light+7.0*PI/6.0)/(4.0*PI/6.0))+1.0, 3.0)); // +1 pq os indices estao em ordem 2,0,1 nos arrays
 		float ang*/
@@ -572,18 +580,18 @@ FRAGMENT_SHADER_CODE
 		vec2 point;
 		float sh;
 		if (abs_angle < 45.0 * PI / 180.0) {
-			point = light_vec;
+			point = shadow_vec;
 			sh = 0.0 + (1.0 / 8.0);
 		} else if (abs_angle > 135.0 * PI / 180.0) {
-			point = -light_vec;
+			point = -shadow_vec;
 			sh = 0.5 + (1.0 / 8.0);
 		} else if (angle_to_light > 0.0) {
 
-			point = vec2(light_vec.y, -light_vec.x);
+			point = vec2(shadow_vec.y, -shadow_vec.x);
 			sh = 0.25 + (1.0 / 8.0);
 		} else {
 
-			point = vec2(-light_vec.y, light_vec.x);
+			point = vec2(-shadow_vec.y, shadow_vec.x);
 			sh = 0.75 + (1.0 / 8.0);
 		}