From 3ebdfda1966ac989bcf90b42627f533cf5643a57 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Sun, 9 Nov 2025 22:30:27 -0600
Subject: [PATCH] particle_oriented_animated_quad_vbuf_pixel_shader: implement
 particle reset

---
 ...iented_animated_quad_vbuf_pixel_shader.cpp |  12 +++--
 src/particle_physics.fs.asm                   |  48 +++++++++++++++---
 src/particle_physics.fs.bin                   | Bin 216 -> 336 bytes
 3 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/src/particle_oriented_animated_quad_vbuf_pixel_shader.cpp b/src/particle_oriented_animated_quad_vbuf_pixel_shader.cpp
index 564fb79..5676423 100644
--- a/src/particle_oriented_animated_quad_vbuf_pixel_shader.cpp
+++ b/src/particle_oriented_animated_quad_vbuf_pixel_shader.cpp
@@ -1158,15 +1158,17 @@ int _floatbuffer(const shaders& shaders,
 
   // fragment constants
   //const vec3 velocity_scale = vec3(0.003f, 0.01f, 0.003f);
-  const vec3 velocity_scale = vec3(0.09f, 0.50f, 0.09f);
-  const float delta_age = 0.01f;
+  const vec3 velocity_scale = vec3(0.9f, 5.0f, 0.9f);
+  const float delta_age = -0.01f;
   const float velocity_attenuation = -0.6f; // multiplied by velocity.y after bounce
   const float gravity = -0.04f;
+  const float max_age = 3.0f;
+  const float reset_radius = 20.0f;
   const float fragment_consts[] = {
     // 0:
     velocity_scale.x, velocity_scale.y, velocity_scale.z, delta_age,
     // 1:
-    velocity_attenuation, gravity, 0, 0,
+    velocity_attenuation, gravity, max_age, reset_radius,
   };
   int fragment_consts_length = (sizeof (fragment_consts)) / (sizeof (fragment_consts[0]));
   ib_ga_consts(fragment_consts, fragment_consts_length, 0);
@@ -1307,8 +1309,8 @@ int main()
   int colorbuffer_ix = 0;
   float theta = PI * 0.5;
 
-  const int floatbuffer_width = 8;
-  const int floatbuffer_height = 8;
+  const int floatbuffer_width = 64;
+  const int floatbuffer_height = 64;
   floatbuffer_state state = create_floatbuffers(fd, floatbuffer_width * floatbuffer_height);
 
   vertexbuffer_handle = init_particles_vertexbuffer(fd, state.length, &vertexbuffer_ptr);
diff --git a/src/particle_physics.fs.asm b/src/particle_physics.fs.asm
index 6f4cd4c..c570f3f 100644
--- a/src/particle_physics.fs.asm
+++ b/src/particle_physics.fs.asm
@@ -20,7 +20,7 @@
 -- const[0] = { velocity_scale.rgb, delta_age }
 -- gravity = -0.05
 -- velocity_attenuation = -0.7
--- const[1] = { velocity_attenuation, gravity, 0, 0 }
+-- const[1] = { velocity_attenuation, gravity, max_age, 0 }
 
 -- out[0].rgb  : position
 -- out[0].a    : age
@@ -64,14 +64,48 @@ src2.rgb = temp[4] : -- position
 src0.rgb = temp[4] :
   temp[4].g = MAX |src0.0g0| |src0.0g0| ;
 
+--
+-- reset
+--
+
+-- normalize(vec3(velocity.x, 0, velocity.z))
+src0.rgb = temp[1] : -- velocity
+              DP3 src0.r0b src0.r0b ,
+  temp[2].a = DP ;
+src0.a   = temp[2] :
+  temp[2].a   = RSQ |src0.a| ;
+src0.a   = temp[2] ,
+src0.rgb = temp[1] : -- velocity
+  temp[2].rgb = MAD src0.r0b src0.a0a src0.000 ;
+
+-- age = age + max_age
+-- reset__position = reset__position * 20
+src0.a   = temp[0]  , -- age
+src1.rgb = const[1] , -- max_age
+src2.a   = const[1] , -- reset_radius
+src0.rgb = temp[2]  : -- reset__position
+  temp[2].a   = MAD src0.a src0.1 src1.b ,
+  temp[2].rgb = MAD src0.rgb src2.aaa src2.000 ;
+
+-- reset__velocity
+src0.a   = temp[1] , -- delta
+src1.a   = float(64) , -- 2.0
+src0.rgb = temp[1] : -- velocity
+  temp[3].rgb = MAD src0.rab src1.1a1 src1.000 ;
+
 OUT
 src0.a   = temp[4]  , -- update__age
-src0.rgb = temp[4]  : -- update__position
-  out[0].a    = MAX src0.a src0.a ,
-  out[0].rgb  = MAX src0.rgb src0.rgb ;
+src1.a   = temp[2]  , -- reset__age
+src2.a   = temp[0]  , -- age
+src0.rgb = temp[4]  , -- update__position
+src1.rgb = temp[2]  : -- reset__position
+  out[0].a    = CMP src0.a src1.a src2.a ,
+  out[0].rgb  = CMP src0.rgb src1.rgb src2.aaa ;
 
 OUT TEX_SEM_WAIT
 src0.a   = temp[1]  , -- delta
-src0.rgb = temp[5]  : -- update__velocity
-  out[1].a    = MAX src0.a src0.a ,
-  out[1].rgb  = MAX src0.rgb src0.rgb ;
+src2.a   = temp[0]  , -- age
+src0.rgb = temp[5]  , -- update__velocity
+src1.rgb = temp[3]  : -- reset__velocity
+  out[1].a    = MAX src0.a src0.a , -- constant
+  out[1].rgb  = CMP src0.rgb src1.rgb src2.aaa ;
diff --git a/src/particle_physics.fs.bin b/src/particle_physics.fs.bin
index a85c47e6ff8809b42cedab2956f6337f021fb420..279fc2b1f7cade91fddd1f75a9dc518e0bc544af 100644
GIT binary patch
delta 176
zcmcb?c!6ocih2eI1_nk3CXNOWW(r_XWB~Dj04NR;V*+9jSNi}9h+<%{fT#zFH#8N3
zg%lV(85k-U7?@aCfNF&V6b|JwC>%JzprGI>1XIt*z|4`LbRMkUK){oMv4Ncds9KW)
lq(wo=g@Nrr1_Q?fGZ|K(1S<~%2hdR<aRufB2?{`Q1^~9M7U=*0

delta 55
ycmcb>bc1oi3IoOlb_Ny(CJqo*U~*w#K9In`%D}+D3KVAriZMdO6@cOjAaMW-Y6rRi