From f8fcd426a10e0f13f01b899e6eb6b3770b08a192 Mon Sep 17 00:00:00 2001
From: Cameron Reikes <cameronreikes@gmail.com>
Date: Mon, 3 Jul 2023 22:22:52 -0700
Subject: [PATCH] Encoding and decoding of float into normalied float vec4

---
 armature.glsl | 14 +++++++++++---
 main.c        | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/armature.glsl b/armature.glsl
index 884436e..804c146 100644
--- a/armature.glsl
+++ b/armature.glsl
@@ -17,6 +17,13 @@ uniform vs_params {
 };
 uniform sampler2D bones_tex;
 
+float decode_normalized_float32(vec4 v)
+{
+	float sign = 2.0 * v.x - 1.0;
+
+	return sign * (v.z*255.0 + v.y);
+}
+
 // in textures, color elements are delivered as unsigend normalize floats
 // in [0, 1]. This makes them into [-1, 1] as the bone matrices require 
 // such values to be correct
@@ -31,13 +38,14 @@ vec4 make_signed_again(vec4 v) {
 void main() {
 	vec4 total_position = vec4(0.0f);
 
-	for(int i = 0; i < 4; i++)
+	for(int bone_influence_index = 0; bone_influence_index < 4; bone_influence_index++)
 	{
-		float index_float = indices_in[i];
+		float index_float = indices_in[bone_influence_index];
 		int index = int(index_float * 65535.0);
-		float weight = weights_in[i];
+		float weight = weights_in[bone_influence_index];
 
 		float y_coord = (0.5 + index)/bones_tex_size.y;
+		
 		vec4 col0 = texture(bones_tex, vec2((0.5 + 0)/bones_tex_size.x, y_coord));
 		vec4 col1 = texture(bones_tex, vec2((0.5 + 1)/bones_tex_size.x, y_coord));
 		vec4 col2 = texture(bones_tex, vec2((0.5 + 2)/bones_tex_size.x, y_coord));
diff --git a/main.c b/main.c
index fd8b1ce..1e8eb55 100644
--- a/main.c
+++ b/main.c
@@ -2705,6 +2705,41 @@ Mat4 get_animated_bone_transform(Bone *bone, float time)
 	return M4D(1.0f);
 }
 
+typedef struct
+{
+	MD_u8 rgba[4];
+} PixelData;
+
+PixelData encode_normalized_float32(float to_encode)
+{
+	Vec4 to_return_vector = {0};
+
+	// x is just -1.0f or 1.0f, encoded as a [0,1] normalized float. 
+	if(to_encode < 0.0f) to_return_vector.x = -1.0f;
+	else to_return_vector.x = 1.0f;
+	to_return_vector.x = to_return_vector.x / 2.0f + 0.5f;
+
+	float without_sign = fabsf(to_encode);
+	to_return_vector.y = without_sign - floorf(without_sign);
+
+	to_return_vector.z = fabsf(to_encode) - to_return_vector.y;
+	assert(to_return_vector.z < 255.0f);
+	to_return_vector.z /= 255.0f;
+
+	// w is unused for now
+
+	PixelData to_return = {0};
+
+	for(int i = 0; i < 4; i++)
+	{
+		assert(0.0f <= to_return_vector.Elements[i] && to_return_vector.Elements[i] <= 1.0f);
+		to_return.rgba[i] = (MD_u8)(to_return_vector.Elements[i] * 255.0f);
+	}
+
+	return to_return;
+}
+
+
 void draw_armature(Mat4 view, Mat4 projection, Transform t, Armature *armature, float elapsed_time)
 {
 	MD_ArenaTemp scratch = MD_GetScratch(0, 0);