grid is not really working

2 files changed, 81 insertions, 3 deletions

diff --git a/assets/shaders/grid.frag b/assets/shaders/grid.frag
index 06eebc3..6cf8a7c 100644
--- a/assets/shaders/grid.frag
+++ b/assets/shaders/grid.frag
@@ -2,6 +2,59 @@
 
 out vec4 FragColor;
 
+in float near; //0.01
+in float far; //100
+in vec3 nearPoint;
+in vec3 farPoint;
+in mat4 fragView;
+in mat4 fragProj;
+
+// void main() {
+//     // FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+//     float t = -nearPoint.y / (farPoint.y - nearPoint.y);
+//     if (t > 0) {
+//         FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+//     } else {
+//         FragColor = vec4(0.0);
+//     }
+//     // FragColor = vec4(1.0, 0.0, 0.0, 1.0 * float(t > 0)); // opacity = 1 when t > 0, opacity = 0 otherwise
+// }
+
+vec4 grid(vec3 fragPos3D, float scale, bool drawAxis) {
+    vec2 coord = fragPos3D.xz * scale;
+    vec2 derivative = fwidth(coord);
+    vec2 grid = abs(fract(coord - 0.5) - 0.5) / derivative;
+    float line = min(grid.x, grid.y);
+    float minimumz = min(derivative.y, 1);
+    float minimumx = min(derivative.x, 1);
+    vec4 color = vec4(0.2, 0.2, 0.2, 1.0 - min(line, 1.0));
+    // z axis
+    if(fragPos3D.x > -0.1 * minimumx && fragPos3D.x < 0.1 * minimumx)
+        color.z = 1.0;
+    // x axis
+    if(fragPos3D.z > -0.1 * minimumz && fragPos3D.z < 0.1 * minimumz)
+        color.x = 1.0;
+    return color;
+}
+float computeDepth(vec3 pos) {
+    vec4 clip_space_pos = fragProj * fragView * vec4(pos.xyz, 1.0);
+    return (clip_space_pos.z / clip_space_pos.w);
+}
+float computeLinearDepth(vec3 pos) {
+    vec4 clip_space_pos = fragProj * fragView * vec4(pos.xyz, 1.0);
+    float clip_space_depth = (clip_space_pos.z / clip_space_pos.w) * 2.0 - 1.0; // put back between -1 and 1
+    float linearDepth = (2.0 * near * far) / (far + near - clip_space_depth * (far - near)); // get linear value between 0.01 and 100
+    return linearDepth / far; // normalize
+}
 void main() {
-    FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+    float t = -nearPoint.y / (farPoint.y - nearPoint.y);
+    vec3 fragPos3D = nearPoint + t * (farPoint - nearPoint);
+
+    gl_FragDepth = computeDepth(fragPos3D);
+
+    float linearDepth = computeLinearDepth(fragPos3D);
+    float fading = max(0, (0.5 - linearDepth));
+
+    FragColor = (grid(fragPos3D, 10, true) + grid(fragPos3D, 1, true))* float(t > 0); // adding multiple resolution for the grid
+    FragColor.a *= fading;
 }
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diff --git a/assets/shaders/grid.vert b/assets/shaders/grid.vert
index bdfa477..592cbfc 100644
--- a/assets/shaders/grid.vert
+++ b/assets/shaders/grid.vert
@@ -6,12 +6,37 @@ uniform Camera {
   vec4 viewPos;
 } cam;
 
+out vec3 nearPoint;
+out vec3 farPoint;
+out float near;
+out float far;
+out mat4 fragView;
+out mat4 fragProj;
+
 // Grid position are in xy clipped space
 vec3 gridPlane[6] = vec3[](
     vec3(1, 1, 0), vec3(-1, -1, 0), vec3(-1, 1, 0),
     vec3(-1, -1, 0), vec3(1, 1, 0), vec3(1, -1, 0)
 );
-// normal vertice projection
+
+vec3 UnprojectPoint(float x, float y, float z, mat4 view, mat4 projection) {
+    mat4 viewInv = inverse(view);
+    mat4 projInv = inverse(projection);
+    vec4 unprojectedPoint =  viewInv * projInv * vec4(x, y, z, 1.0);
+    return unprojectedPoint.xyz / unprojectedPoint.w;
+}
+
+// normal vertex projection
 void main() {
-    gl_Position = cam.proj * cam.view * vec4(gridPlane[gl_VertexID].xyz, 1.0);
+    // gl_Position = cam.proj * cam.view * vec4(gridPlane[gl_VertexID].xyz, 1.0);
+    vec3 p = gridPlane[gl_VertexID].xyz;
+    nearPoint = UnprojectPoint(p.x, p.y, -1.0, cam.view, cam.proj).xyz; // unprojecting on the near plane
+    farPoint = UnprojectPoint(p.x, p.y, 1.0, cam.view, cam.proj).xyz; // unprojecting on the far plane
+
+    fragView = cam.view;
+    fragProj = cam.proj;
+    near = 0.01;
+    far = 100.0;
+
+    gl_Position = vec4(p, 1.0); // using directly the clipped coordinates
 }
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