1 files changed, 82 insertions, 0 deletions
diff --git a/src/sdf.rs b/src/sdf.rs
new file mode 100644
index 0000000..51d85cc
--- /dev/null
+++ b/src/sdf.rs
@@ -0,0 +1,82 @@
+#![allow(dead_code)] // @TODO @TEMPORARY
+
+use std::fmt::Write;
+
+// we're only writing numbers and strings so write! should never fail.
+macro_rules! write_str {
+	($( $arg:tt )*) => { write!($($arg)*).unwrap() }
+}
+
+enum R3ToR3 {
+	Identity,
+	Translate([f32; 3])
+}
+
+enum RToR {
+	Identity,
+	Add(f32)
+}
+
+pub struct Sdf {
+	pre: R3ToR3,
+	post: RToR
+}
+
+impl RToR {
+	/// treats `v<*initial value of var_idx>` as the input, and puts the output in `v<final value of *var_idx>`.
+	fn to_glsl(&self, code: &mut String, var_idx: &mut u32) {
+		use RToR::*;
+		let input = *var_idx;
+		
+		match self {
+			Identity => {}, // no code
+			Add(x) => {
+				*var_idx += 1;
+				let output = *var_idx;
+				write_str!(code, "float v{output} = v{input} + {x};\n");
+			}
+		}
+	}
+}
+
+impl R3ToR3 {
+	/// treats `v<*initial value of var_idx>` as the input, and puts the output in `v<final value of *var_idx>`.
+	fn to_glsl(&self, code: &mut String, var_idx: &mut u32) {
+		use R3ToR3::*;
+		let input = *var_idx;
+		
+		match self {
+			Identity => {}, // no code
+			Translate([x, y, z]) => {
+				*var_idx += 1;
+				let output = *var_idx;
+				write_str!(code, "vec3 v{output} = v{input} + vec3({x}, {y}, {z});\n");
+			},
+		}
+	}
+}
+
+impl Sdf {
+	/// test sphere
+	pub fn sphere() -> Self {
+		Self {
+			pre: R3ToR3::Identity,
+			post: RToR::Identity
+		}
+	}
+
+	/// appends some glsl code including a function `float sdf(vec3 p) { ... }`
+	pub fn to_glsl(&self, code: &mut String) {
+		code.push_str("float sdf(vec3 p) {\n");
+		// don't start out right next to the origin, since weird stuff might be happening there
+		let origin_dist: f32 = 2.0;
+		write_str!(code, "vec3 v0 = p - vec3(0,0,-{}.);\n", origin_dist);
+		let mut var_idx = 0;
+		self.pre.to_glsl(code, &mut var_idx);
+		write_str!(code, "float v{} = length(v{}) - 1.0;\n", var_idx + 1, var_idx);
+		var_idx += 1;
+		self.post.to_glsl(code, &mut var_idx);
+		write_str!(code, "return v{var_idx};\n");
+		code.push('}');
+	}
+}