screen-space sobel filter

main.lua

@@ -17,8 +17,35 @@ local scene_sci_fi_ship = require 'scene.sci_fi_ship.sci_fi_ship'
 
 local node_state
 
+local g_position_canvas
+local g_normal_canvas
+
+local screen_index_buffer
+local screen_shader
+
+local load_screen_index_buffer = function()
+   local screen_index_data = love.data.newByteData(3 * 2 * 4)
+   local ptr = ffi.cast('uint32_t*', screen_index_data:getFFIPointer())
+   ptr[0] = 0
+   ptr[1] = 1
+   ptr[2] = 2
+
+   ptr[3] = 0
+   ptr[4] = 2
+   ptr[5] = 3
+   screen_index_buffer = love.graphics.newBuffer("uint32", screen_index_data, { index = true, usage = "static" })
+end
+
+local load_screen_shader = function()
+   load_screen_index_buffer()
+
+   local pixel_data = love.filesystem.newFileData("pixel_sobel.glsl")
+   local vertex_data = love.filesystem.newFileData("vertex_sobel.glsl")
+   screen_shader = love.graphics.newShader(pixel_data, vertex_data)
+end
+
 function love.load(args)
-   love.window.setMode(1024, 1024, {depth=true})
+   love.window.setMode(1024, 1024, {depth=true, resizable=false})
 
    local scene = scene_sci_fi_ship
 
@@ -28,6 +55,16 @@ function love.load(args)
    collada_scene.load_buffers(idx_path, vtx_path, vjw_path)
    collada_scene.load_images("scene/sci_fi_ship", scene.descriptor.images)
    node_state = collada_scene_node_state(scene.descriptor.nodes)
+
+   ----------------------------------------------------------------------
+   -- canvas
+   ----------------------------------------------------------------------
+
+   g_position_canvas = love.graphics.newCanvas(1024, 1024, {format = "rgba32f"})
+   g_normal_canvas = love.graphics.newCanvas(1024, 1024, {format = "rgba32f"})
+   g_color_canvas = love.graphics.newCanvas(1024, 1024, {format = "rgba32f"})
+
+   load_screen_shader()
 end
 
 local rotation = 0.0
@@ -49,15 +86,33 @@ function love.draw()
                                 vec3(0.0, 0.0, 13.41141),
                                 vec3(0, 0, 1))
 
-   local world1 = mat4.rotation_x(rotation)
+   local world1 = mat4.rotation_z(rotation)
    local world2 = mat4.rotation_z(rotation * 0.5)
    --local world3 = mat4.translation(0, 0, -0.5)
+   rotation = rotation + 0.01
 
    local transform = view * projection
 
    collada_scene_animate.update(t, node_state)
    t = t + 0.016
 
+   love.graphics.setBlendMode("replace", "premultiplied")
    love.graphics.setDepthMode("less", true)
+   love.graphics.setCanvas({
+         g_color_canvas,
+         g_position_canvas,
+         g_normal_canvas,
+         depth = true
+   })
+   love.graphics.clear(
+      {0.0, 0.0, 0.0, 1.0},
+      {0.0, 0.0, 0.0, 1.0},
+      {0.0, 0.0, 0.0, 1.0})
    collada_scene.draw_nodes(node_state, transform)
+
+   love.graphics.setCanvas()
+   love.graphics.setShader(screen_shader)
+   screen_shader:send("g_normal_sampler", g_normal_canvas)
+   screen_shader:send("g_color_sampler", g_color_canvas)
+   love.graphics.drawFromShader(screen_index_buffer, 3 * 2, 1, 1)
 end

pixel.glsl

@@ -19,7 +19,9 @@ uniform vec4 view_position;
 uniform vec4 light_position;
 uniform ivec4 texture_channel;
 
-out vec4 out_color;
+layout (location = 0) out vec4 g_color;
+layout (location = 1) out vec4 g_position;
+layout (location = 2) out vec4 g_normal;
 
 void pixelmain()
 {
@@ -61,5 +63,7 @@ void pixelmain()
   color += diffuse.xyz * diffuse_intensity;
   color += specular.xyz * specular_intensity * 0.3;
 
-  out_color = vec4(color, 1.0);
+  g_position = vec4(PixelWorldPosition.xyz * 0.0005 + 0.5, 0.0);
+  g_normal = vec4(normal * 0.5 + 0.5, PixelWorldPosition.z * 0.001 + 0.5);
+  g_color = vec4(color, 1.0);
 }

pixel_sobel.glsl

@@ -0,0 +1,60 @@
+#pragma language glsl3
+
+uniform sampler2D g_position_sampler;
+uniform sampler2D g_normal_sampler;
+uniform sampler2D g_color_sampler;
+
+varying vec4 PixelTexture;
+
+out vec4 out_color;
+
+mat3 sobel_x = mat3( 1.0,  2.0,  1.0,
+                     0.0,  0.0,  0.0,
+                    -1.0, -2.0, -1.0);
+mat3 sobel_y = mat3(1.0, 0.0, -1.0,
+                    2.0, 0.0, -2.0,
+                    1.0, 0.0, -1.0);
+
+float sobel(mat3 K)
+{
+
+  float sx = dot(sobel_x[0], K[0]) + dot(sobel_x[1], K[1]) + dot(sobel_x[2], K[2]);
+  float sy = dot(sobel_y[0], K[0]) + dot(sobel_y[1], K[1]) + dot(sobel_y[2], K[2]);
+  float edge = sqrt(pow(sx, 2.0) + pow(sy, 2.0));
+  //float edge = max(sx, sy);
+  return edge;
+}
+
+float kernel()
+{
+  mat3 K;
+  mat3 Kz;
+  //mat3 Kx;
+  //mat3 Ky;
+  //mat3 Kz;
+  for (int x = 0; x < 3; x++) {
+    for (int y = 0; y < 3; y++) {
+      vec4 sample = texelFetch(g_normal_sampler, ivec2(gl_FragCoord) + ivec2(x-1, y-1), 0);
+      //Kx[x][y] = sample.x;
+      //Ky[x][y] = sample.y;
+      //Kz[x][y] = sample.z;
+      K[x][y] = length(sample.xyz);
+    }
+  }
+
+  //return max(sobel(Kx), max(sobel(Ky), sobel(Kz)));
+  return float(sobel(K) < 0.1);
+}
+
+void pixelmain()
+{
+  vec4 color = texelFetch(g_color_sampler, ivec2(gl_FragCoord), 0);
+
+  if (color.xyz == vec3(0, 0, 0)) {
+    out_color = vec4(0.1, 0.1, 0.2, 1.0);
+  } else {
+    float edge = kernel();
+    out_color = vec4(edge * color.xyz, 1.0);
+    //out_color = vec4(edge, edge, edge, 1.0);
+  }
+}

vertex_sobel.glsl

@@ -0,0 +1,17 @@
+#pragma language glsl3
+
+const vec4 vtx[4] = vec4[](vec4(-1.0,  1.0, 0.0, 1.0),  // tl
+                           vec4( 1.0,  1.0, 0.0, 1.0),  // tr
+                           vec4( 1.0, -1.0, 0.0, 1.0),  // br
+                           vec4(-1.0, -1.0, 0.0, 1.0)); // bl
+
+varying vec4 PixelTexture;
+
+void vertexmain()
+{
+  vec4 vertex = vtx[gl_VertexID];
+
+  PixelTexture = vec4(vertex.xy * vec2(0.5, -0.5) + 0.5, 0, 0);
+
+  love_Position = vertex;
+}