From 99947c190c74bbcc3f3548b8f689960af87b04a9 Mon Sep 17 00:00:00 2001
From: FMS-Cat <yutaka.obuchi@gmail.com>
Date: Sat, 27 Mar 2021 20:50:08 +0900
Subject: [PATCH] performance: hey, raymarch can be started from the
 intersection

---
 src/shaders/raymarch-object.vert | 5 ++++-
 src/shaders/wobbleball.frag      | 4 +++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/shaders/raymarch-object.vert b/src/shaders/raymarch-object.vert
index 8a53c1e..6d915f0 100644
--- a/src/shaders/raymarch-object.vert
+++ b/src/shaders/raymarch-object.vert
@@ -2,6 +2,8 @@
 
 layout (location = 0) in vec3 position;
 
+out vec4 vPosition;
+
 uniform vec2 resolution;
 uniform mat4 projectionMatrix;
 uniform mat4 viewMatrix;
@@ -10,7 +12,8 @@ uniform mat4 modelMatrix;
 // ------
 
 void main() {
-  vec4 outPos = projectionMatrix * viewMatrix * modelMatrix * vec4( position, 1.0 );
+  vPosition = modelMatrix * vec4( position, 1.0 );
+  vec4 outPos = projectionMatrix * viewMatrix * vPosition;
 
   outPos.x *= resolution.y / resolution.x;
   gl_Position = outPos;
diff --git a/src/shaders/wobbleball.frag b/src/shaders/wobbleball.frag
index 35cbd3a..b9d6520 100644
--- a/src/shaders/wobbleball.frag
+++ b/src/shaders/wobbleball.frag
@@ -21,6 +21,8 @@ const float TAU = PI * 2.0;
   layout (location = 3) out vec4 fragWTF;
 #endif
 
+in vec4 vPosition;
+
 #ifdef SHADOW
   out vec4 fragColor;
 #endif
@@ -111,7 +113,7 @@ void main() {
   vec3 rayOri = divideByW( inversePVM * vec4( p, 0.0, 1.0 ) );
   vec3 farPos = divideByW( inversePVM * vec4( p, 1.0, 1.0 ) );
   vec3 rayDir = normalize( farPos - rayOri );
-  float rayLen = cameraNearFar.x;
+  float rayLen = length( vPosition.xyz - cameraPos );
   vec3 rayPos = rayOri + rayDir * rayLen;
   float dist;