actually memory is bad

Signed-off-by: lizzie <lizzie@eden-emu.dev>

src/video_core/host_shaders/present_lanczos.frag

@@ -9,22 +9,28 @@ layout (location = 0) in vec2 frag_tex_coord;
 layout (location = 0) out vec4 color;
 layout (binding = 0) uniform sampler2D color_texture;
 
-// precomputed kernel
-const float w_kernel[49] = float[] (
-    -0.238811f, 0.531959f, 0.961865f, 1.000000f, 0.961865f, 0.531959f, -0.238811f, 0.531959f, 0.957419f, 0.313883f, -0.000000f, 0.313883f, 0.957419f, 0.531959f, 0.961865f, 0.313883f, -0.322602f, 0.000000f, -0.322602f, 0.313883f, 0.961865f, 1.000000f, -0.000000f, 0.000000f, 1.000000f, 0.000000f, -0.000000f, 1.000000f, 0.961865f, 0.313883f, -0.322602f, 0.000000f, -0.322602f, 0.313883f, 0.961865f, 0.531959f, 0.957419f, 0.313883f, -0.000000f, 0.313883f, 0.957419f, 0.531959f, -0.238811f, 0.531959f, 0.961865f, 1.000000f, 0.961865f, 0.531959f, -0.238811f
-);
-const vec2 w_pos[49] = vec2[] (
-    vec2(-0.750000f, -0.750000f), vec2(-0.750000f, -0.500000f), vec2(-0.750000f, -0.250000f), vec2(-0.750000f, 0.000000f), vec2(-0.750000f, 0.250000f), vec2(-0.750000f, 0.500000f), vec2(-0.750000f, 0.750000f), vec2(-0.500000f, -0.750000f), vec2(-0.500000f, -0.500000f), vec2(-0.500000f, -0.250000f), vec2(-0.500000f, 0.000000f), vec2(-0.500000f, 0.250000f), vec2(-0.500000f, 0.500000f), vec2(-0.500000f, 0.750000f), vec2(-0.250000f, -0.750000f), vec2(-0.250000f, -0.500000f), vec2(-0.250000f, -0.250000f), vec2(-0.250000f, 0.000000f), vec2(-0.250000f, 0.250000f), vec2(-0.250000f, 0.500000f), vec2(-0.250000f, 0.750000f), vec2(0.000000f, -0.750000f), vec2(0.000000f, -0.500000f), vec2(0.000000f, -0.250000f), vec2(0.000000f, 0.000000f), vec2(0.000000f, 0.250000f), vec2(0.000000f, 0.500000f), vec2(0.000000f, 0.750000f), vec2(0.250000f, -0.750000f), vec2(0.250000f, -0.500000f), vec2(0.250000f, -0.250000f), vec2(0.250000f, 0.000000f), vec2(0.250000f, 0.250000f), vec2(0.250000f, 0.500000f), vec2(0.250000f, 0.750000f), vec2(0.500000f, -0.750000f), vec2(0.500000f, -0.500000f), vec2(0.500000f, -0.250000f), vec2(0.500000f, 0.000000f), vec2(0.500000f, 0.250000f), vec2(0.500000f, 0.500000f), vec2(0.500000f, 0.750000f), vec2(0.750000f, -0.750000f), vec2(0.750000f, -0.500000f), vec2(0.750000f, -0.250000f), vec2(0.750000f, 0.000000f), vec2(0.750000f, 0.250000f), vec2(0.750000f, 0.500000f), vec2(0.750000f, 0.750000f)
-);
-const float w_sum = 21.045683f;
+#define PI 3.1415926535897932384626433
+float sinc(float x) {
+    return x == 0.0f ? 1.0f : sin(PI * x) / (PI * x);
+}
+float lanczos(vec2 v, float a) {
+    float d = length(v);
+    return sinc(d) / sinc(d / a);
+}
 vec4 textureLanczos(sampler2D textureSampler, vec2 p) {
     vec3 c_sum = vec3(0.0f);
+    float w_sum = 0.0f;
     vec2 res = vec2(textureSize(textureSampler, 0));
     vec2 cc = floor(p * res) / res;
-    for (int i = 0; i < 49; i++) { // kernel size = (r * 2 + 1) ^ 2
-        vec2 kp = w_pos[i] / res;
+    // kernel size = (2r + 1)^2
+    const int r = 3; //radius (1 = 3 steps)
+    for (int x = -r; x <= r; x++)
+        for (int y = -r; y <= r; y++) {
+            vec2 kp = 0.5f * (vec2(x, y) / res); // 0.5 = half-pixel level resampling
             vec2 uv = cc + kp;
-        c_sum += w_kernel[i] * texture(textureSampler, p + kp).rgb;
+            float w = lanczos(kp, float(r));
+            c_sum += w * texture(textureSampler, p + kp).rgb;
+            w_sum += w;
         }
     return vec4(c_sum / w_sum, 1.0f);
 }