refactor: transparent render (#14)

* fix(renderer): defer uniform location retrieval and add view matrix in outline rendering

* refactor(gameplay): encapsulate per-type vertex data into VertexData struct

* feat(rendering): separate transparent blocks into discard and blend modes

* feat(renderer): implement order-independent transparency

* fix(shaders): reduce alpha discard threshold to 0.8

assets/shaders/block_accumulation_f_shader.glsl

@@ -0,0 +1,28 @@
+#version 460
+
+layout (location = 0) out vec4 accum;
+layout (location = 1) out float reveal;
+
+in vec2 tc;
+flat in int tex_layer;
+in float v_depth;
+layout (binding = 0) uniform sampler2DArray samp;
+
+float weight(float z, float a) {
+    float intermediate = 0.03 / (1e-5 + pow(z / 200.0, 4.0));
+    
+    return a * clamp(intermediate, 1e-2, 3e2);
+}
+
+void main() {
+    vec4 color = texture(samp, vec3(tc, tex_layer));
+    float alpha = color.a;
+    if (alpha < 1e-4) discard;
+
+
+    float w = weight(v_depth, alpha);
+
+    accum = vec4(color.rgb * alpha * w, alpha * w);
+
+    reveal = alpha;
+}