From 5f51d26eca1e6d2cc10e1e105972e932e3366e7f Mon Sep 17 00:00:00 2001
From: Karsten Schmidt <k@thi.ng>
Date: Mon, 8 Aug 2022 13:31:28 +0200
Subject: [PATCH] feat(webgl): update Multipass

- auto-enable EXT_float_blend extension for float outputs
  (this silences warnings on Firefox, Chrome seemed fine)
- add Multipass.singlePass() to selectively execute single shader passes
---
 packages/webgl/src/api/multipass.ts |  7 +++++++
 packages/webgl/src/multipass.ts     | 12 ++++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/packages/webgl/src/api/multipass.ts b/packages/webgl/src/api/multipass.ts
index 28ab2344c5..4ab8e432d4 100644
--- a/packages/webgl/src/api/multipass.ts
+++ b/packages/webgl/src/api/multipass.ts
@@ -20,6 +20,13 @@ export interface Multipass {
 	start(): void;
 	stop(): void;
 	update(time?: number): void;
+	/**
+	 * Executes a single shader pass only.
+	 *
+	 * @param id
+	 * @param time
+	 */
+	singlePass(id: number, time: number): void;
 
 	fbos: IFbo[];
 	models: ModelSpec[];
diff --git a/packages/webgl/src/multipass.ts b/packages/webgl/src/multipass.ts
index 57fffc17b0..5ecf5024dd 100644
--- a/packages/webgl/src/multipass.ts
+++ b/packages/webgl/src/multipass.ts
@@ -38,7 +38,8 @@ export const defMultiPass = (opts: MultipassOpts) => {
 	const passes = initPasses(opts, textures);
 	const fbos = initBuffers(opts, textures, useMainBuffer);
 
-	const drawPass = (i: number, time: number) => {
+	const drawPass = (i: number, time: number, isFBO = true) => {
+		isFBO && fbos[i].bind();
 		const spec = opts.passes[i];
 		const pass = passes[i];
 		const shader = pass.shader;
@@ -49,15 +50,14 @@ export const defMultiPass = (opts: MultipassOpts) => {
 		shader.uniforms.time && (pass.uniforms!.time = time);
 		gl.viewport(0, 0, size[0], size[1]);
 		draw(pass);
+		isFBO && fbos[i].unbind();
 	};
 
 	const update = (time: number) => {
 		for (let i = 0; i < fbos.length; i++) {
-			fbos[i].bind();
 			drawPass(i, time);
-			fbos[i].unbind();
 		}
-		useMainBuffer && drawPass(numPasses - 1, time);
+		useMainBuffer && drawPass(numPasses - 1, time, false);
 	};
 
 	const updateRAF = () => {
@@ -84,6 +84,9 @@ export const defMultiPass = (opts: MultipassOpts) => {
 		update(time: number) {
 			update(time);
 		},
+		singlePass(i: number, time: number) {
+			drawPass(i, time, i < fbos.length);
+		},
 		passes: opts.passes,
 		fbos,
 		models: passes,
@@ -162,6 +165,7 @@ const initShader = (
 	if (floatOut) {
 		ext[isGL2 ? "EXT_color_buffer_float" : "WEBGL_color_buffer_float"] =
 			"require";
+		isGL2 && (ext["EXT_float_blend"] = "require");
 	}
 	return defShader(gl, spec);
 };