DRW: Remove view vectors

This is part of the effor to simplify the View struct in order to implement
multiview rendering.

The viewvecs can easilly be replace by projection matrix operation.
Even if slightly more complex, there is no performance impact.

1 files changed, 20 insertions, 24 deletions

diff --git a/source/blender/draw/intern/shaders/common_view_lib.glsl b/source/blender/draw/intern/shaders/common_view_lib.glsl
index 2382337e782..a09bccc4f2e 100644
--- a/source/blender/draw/intern/shaders/common_view_lib.glsl
+++ b/source/blender/draw/intern/shaders/common_view_lib.glsl
@@ -17,10 +17,6 @@ layout(std140) uniform viewBlock
   mat4 ProjectionMatrixInverse;
 
   vec4 clipPlanes[6];
-
-  /* View frustum corners [NDC(-1.0, -1.0, -1.0) & NDC(1.0, 1.0, 1.0)].
-   * Fourth components are near and far values. */
-  vec4 ViewVecs[2];
 };
 
 #endif /* USE_GPU_SHADER_CREATE_INFO */
@@ -34,9 +30,6 @@ layout(std140) uniform viewBlock
 #define IS_DEBUG_MOUSE_FRAGMENT (ivec2(gl_FragCoord) == drw_view.mouse_pixel)
 #define IS_FIRST_INVOCATION (gl_GlobalInvocationID == uvec3(0))
 
-#define ViewNear (ViewVecs[0].w)
-#define ViewFar (ViewVecs[1].w)
-
 #define cameraForward ViewMatrixInverse[2].xyz
 #define cameraPos ViewMatrixInverse[3].xyz
 vec3 cameraVec(vec3 P)
@@ -310,24 +303,26 @@ float buffer_depth(bool is_persp, float z, float zf, float zn)
 
 float get_view_z_from_depth(float depth)
 {
+  float d = 2.0 * depth - 1.0;
   if (ProjectionMatrix[3][3] == 0.0) {
-    float d = 2.0 * depth - 1.0;
-    return -ProjectionMatrix[3][2] / (d + ProjectionMatrix[2][2]);
+    d = -ProjectionMatrix[3][2] / (d + ProjectionMatrix[2][2]);
   }
   else {
-    return ViewVecs[0].z + depth * ViewVecs[1].z;
+    d = (d - ProjectionMatrix[3][2]) / ProjectionMatrix[2][2];
   }
+  return d;
 }
 
 float get_depth_from_view_z(float z)
 {
+  float d;
   if (ProjectionMatrix[3][3] == 0.0) {
-    float d = (-ProjectionMatrix[3][2] / z) - ProjectionMatrix[2][2];
-    return d * 0.5 + 0.5;
+    d = (-ProjectionMatrix[3][2] / z) - ProjectionMatrix[2][2];
   }
   else {
-    return (z - ViewVecs[0].z) / ViewVecs[1].z;
+    d = ProjectionMatrix[2][2] * z + ProjectionMatrix[3][2];
   }
+  return d * 0.5 + 0.5;
 }
 
 vec2 get_uvs_from_view(vec3 view)
@@ -338,12 +333,9 @@ vec2 get_uvs_from_view(vec3 view)
 
 vec3 get_view_space_from_depth(vec2 uvcoords, float depth)
 {
-  if (ProjectionMatrix[3][3] == 0.0) {
-    return vec3(ViewVecs[0].xy + uvcoords * ViewVecs[1].xy, 1.0) * get_view_z_from_depth(depth);
-  }
-  else {
-    return ViewVecs[0].xyz + vec3(uvcoords, depth) * ViewVecs[1].xyz;
-  }
+  vec3 ndc = vec3(uvcoords, depth) * 2.0 - 1.0;
+  vec4 p = ProjectionMatrixInverse * vec4(ndc, 1.0);
+  return p.xyz / p.w;
 }
 
 vec3 get_world_space_from_depth(vec2 uvcoords, float depth)
@@ -351,14 +343,18 @@ vec3 get_world_space_from_depth(vec2 uvcoords, float depth)
   return (ViewMatrixInverse * vec4(get_view_space_from_depth(uvcoords, depth), 1.0)).xyz;
 }
 
-vec3 get_view_vector_from_screen_uv(vec2 uv)
+vec3 get_view_vector_from_screen_uv(vec2 uvcoords)
 {
   if (ProjectionMatrix[3][3] == 0.0) {
-    return normalize(vec3(ViewVecs[0].xy + uv * ViewVecs[1].xy, 1.0));
-  }
-  else {
-    return vec3(0.0, 0.0, 1.0);
+    vec2 ndc = vec2(uvcoords * 2.0 - 1.0);
+    /* This is the manual inversion of the ProjectionMatrix. */
+    vec3 vV = vec3((-ndc - ProjectionMatrix[2].xy) /
+                       vec2(ProjectionMatrix[0][0], ProjectionMatrix[1][1]),
+                   -ProjectionMatrix[2][2] - ProjectionMatrix[3][2]);
+    return normalize(vV);
   }
+  /* Orthographic case. */
+  return vec3(0.0, 0.0, 1.0);
 }
 
 #endif /* COMMON_VIEW_LIB_GLSL */