Use textureOffset() wherever possible to save some tedious arithmetic.

diff --git a/derivatives.frag b/derivatives.frag
index f5394c37a3f26031ca54d4244824568ae6477af6..e5e355700f56e1197d1ca3cd2326ae346d98a651 100644 (file)
--- a/derivatives.frag
+++ b/derivatives.frag
@@ -4,19 +4,18 @@ in vec2 tc;
 out vec2 derivatives;
 
 uniform sampler2D tex;
-uniform vec2 inv_image_size;
 
 void main()
 {
-       float x_m2 = texture(tex, vec2(tc.x - 2.0 * inv_image_size.x), tc.y).x;
-       float x_m1 = texture(tex, vec2(tc.x -       inv_image_size.x), tc.y).x;
-       float x_p1 = texture(tex, vec2(tc.x +       inv_image_size.x), tc.y).x;
-       float x_p2 = texture(tex, vec2(tc.x + 2.0 * inv_image_size.x), tc.y).x;
+       float x_m2 = textureOffset(tex, tc, ivec2(-2,  0)).x;
+       float x_m1 = textureOffset(tex, tc, ivec2(-1,  0)).x;
+       float x_p1 = textureOffset(tex, tc, ivec2( 1,  0)).x;
+       float x_p2 = textureOffset(tex, tc, ivec2( 2,  0)).x;
 
-       float y_m2 = texture(tex, vec2(tc.x, tc.y - 2.0 * inv_image_size.y)).x;
-       float y_m1 = texture(tex, vec2(tc.x, tc.y -       inv_image_size.y)).x;
-       float y_p1 = texture(tex, vec2(tc.x, tc.y +       inv_image_size.y)).x;
-       float y_p2 = texture(tex, vec2(tc.x, tc.y + 2.0 * inv_image_size.y)).x;
+       float y_m2 = textureOffset(tex, tc, ivec2( 0, -2)).x;
+       float y_m1 = textureOffset(tex, tc, ivec2( 0, -1)).x;
+       float y_p1 = textureOffset(tex, tc, ivec2( 0,  1)).x;
+       float y_p2 = textureOffset(tex, tc, ivec2( 0,  2)).x;
 
        derivatives.x = (x_p1 - x_m1) * (2.0/3.0) + (x_m2 - x_p2) * (1.0/12.0);
        derivatives.y = (y_p1 - y_m1) * (2.0/3.0) + (y_m2 - y_p2) * (1.0/12.0);

diff --git a/flow.cpp b/flow.cpp
index d5e73eccf93c47a16d3ef943612873428bd80402..9bae425004d359345b9ee84f827055e4443cbcd9 100644 (file)
--- a/flow.cpp
+++ b/flow.cpp
@@ -224,7 +224,7 @@ private:
        GLuint sobel_program;
        GLuint sobel_vao;
 
-       GLuint uniform_tex, uniform_image_size, uniform_inv_image_size;
+       GLuint uniform_tex, uniform_image_size;
 };
 
 Sobel::Sobel()
@@ -242,7 +242,6 @@ Sobel::Sobel()
        glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 
        uniform_tex = glGetUniformLocation(sobel_program, "tex");
-       uniform_inv_image_size = glGetUniformLocation(sobel_program, "inv_image_size");
 }
 
 void Sobel::exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_height)
@@ -251,7 +250,6 @@ void Sobel::exec(GLint tex0_view, GLint grad0_tex, int level_width, int level_he
        glBindTextureUnit(0, tex0_view);
        glBindSampler(0, nearest_sampler);
        glProgramUniform1i(sobel_program, uniform_tex, 0);
-       glProgramUniform2f(sobel_program, uniform_inv_image_size, 1.0f / level_width, 1.0f / level_height);
 
        GLuint grad0_fbo;  // TODO: cleanup
        glCreateFramebuffers(1, &grad0_fbo);
@@ -483,7 +481,6 @@ private:
        GLuint derivatives_vao;
 
        GLuint uniform_tex;
-       GLuint uniform_inv_image_size;
 };
 
 Derivatives::Derivatives()
@@ -502,7 +499,6 @@ Derivatives::Derivatives()
        glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
 
        uniform_tex = glGetUniformLocation(derivatives_program, "tex");
-       uniform_inv_image_size = glGetUniformLocation(derivatives_program, "inv_image_size");
 }
 
 void Derivatives::exec(GLuint input_tex, GLuint output_tex, int level_width, int level_height)
@@ -510,7 +506,6 @@ void Derivatives::exec(GLuint input_tex, GLuint output_tex, int level_width, int
        glUseProgram(derivatives_program);
 
        bind_sampler(derivatives_program, uniform_tex, 0, input_tex, nearest_sampler);
-       glProgramUniform2f(derivatives_program, uniform_inv_image_size, 1.0f / level_width, 1.0f / level_height);
 
        GLuint derivatives_fbo;  // TODO: cleanup
        glCreateFramebuffers(1, &derivatives_fbo);

diff --git a/sobel.frag b/sobel.frag
index c4dabd519712465a9d2a5495617ac9c1e2708c5b..518b6f8abcdadb4491b8e1187f6cea3e696fa477 100644 (file)
--- a/sobel.frag
+++ b/sobel.frag
@@ -26,24 +26,16 @@ void main()
        // Computing both directions at once allows us to get away with eight
        // texture samples instead of twelve.
 
-       float x_left   = tc.x - inv_image_size.x;
-       float x_mid    = tc.x; 
-       float x_right  = tc.x + inv_image_size.x;
-
-       float y_top    = tc.y + inv_image_size.y;  // Note the bottom-left coordinate system.
-       float y_mid    = tc.y;
-       float y_bottom = tc.y - inv_image_size.y;
- 
-       float top_left     = texture(tex, vec2(x_left,  y_top)).x;
-       float left         = texture(tex, vec2(x_left,  y_mid)).x;
-       float bottom_left  = texture(tex, vec2(x_left,  y_bottom)).x;
-
-       float top          = texture(tex, vec2(x_mid,   y_top)).x;
-       float bottom       = texture(tex, vec2(x_mid,   y_bottom)).x;
-
-       float top_right    = texture(tex, vec2(x_right, y_top)).x;
-       float right        = texture(tex, vec2(x_right, y_mid)).x;
-       float bottom_right = texture(tex, vec2(x_right, y_bottom)).x;
+       float top_left     = textureOffset(tex, tc, ivec2(-1,  1)).x;  // Note the bottom-left coordinate system.
+       float left         = textureOffset(tex, tc, ivec2(-1,  0)).x;
+       float bottom_left  = textureOffset(tex, tc, ivec2(-1, -1)).x;
+
+       float top          = textureOffset(tex, tc, ivec2( 0,  1)).x;
+       float bottom       = textureOffset(tex, tc, ivec2( 0, -1)).x;
+
+       float top_right    = textureOffset(tex, tc, ivec2( 1,  1)).x;
+       float right        = textureOffset(tex, tc, ivec2( 1,  0)).x;
+       float bottom_right = textureOffset(tex, tc, ivec2( 1, -1)).x;
 
        gradients.x = (top_right + 2.0f * right + bottom_right) - (top_left + 2.0f * left + bottom_left);
        gradients.y = (top_left + 2.0 * top + top_right) - (bottom_left + 2.0f * bottom + bottom_right);