trail rendering basics

[carveJwlIkooP6JGAAIwe30JlM.git] / trail.c

diff --git a/trail.c b/trail.c
new file mode 100644 (file)
index 0000000..bf23b1c
--- /dev/null
+++ b/trail.c
@@ -0,0 +1,159 @@
+#pragma once
+#include "trail.h"
+
+static void trail_system_update( trail_system *sys, f32 dt,
+                                 v3f co, v3f normal, f32 alpha ){
+   /* update existing points and clip dead ones */
+   bool clip_allowed = 1;
+   for( i32 i=0; i<sys->count; i ++ ){
+      i32 i0 = sys->head - sys->count + i;
+      if( i0 < 0 ) i0 += sys->max;
+
+      trail_point *p0 = &sys->array[i0];
+      p0->alpha -= dt/sys->lifetime;
+
+      if( clip_allowed ){
+         if( p0->alpha <= 0.0f )
+            sys->count --;
+         else
+            clip_allowed = 0;
+      }
+   }
+
+   bool add_point = 1;
+   i32 index_current = sys->head;
+   if( sys->count >= 2 ) index_current = sys->head -1;
+
+   i32 index_prev = index_current -1;
+
+   if( index_current < 0 ) index_current += sys->max;
+   if( index_prev    < 0 ) index_prev    += sys->max;
+
+   /* always enforced non-zero distance */
+   if( sys->count >= 1 ){
+      if( v3_dist2( sys->array[index_prev].co, co ) < 0.001f*0.001f )
+         return;
+   }
+
+   /* copy new info in */
+   trail_point *p_current = &sys->array[index_current];
+   v3_copy( co, p_current->co );
+   v3_copy( normal, p_current->normal );
+   p_current->alpha = alpha;
+
+   /* update direction */
+   if( sys->count >= 2 ){
+      trail_point *p_prev = &sys->array[index_prev];
+
+      v3f dir;
+      v3_sub( co, p_prev->co, dir );
+      v3_normalize( dir );
+      v3_cross( dir, normal, p_current->right );
+      v3_copy( p_current->right, p_prev->right );
+
+      /* decide if to prevent split based on user min-distance */
+      if( v3_dist2( p_prev->co, co ) < sys->min_dist*sys->min_dist )
+         add_point = 0;
+   }
+   else 
+      v3_zero( p_current->right );
+
+   if( add_point ){
+      sys->head ++;
+
+      if( sys->head == sys->max )
+         sys->head = 0;
+
+      /* undesirable effect: will remove active points if out of space! */
+      if( sys->count < sys->max )
+         sys->count ++;
+
+      index_current = sys->head;
+   }
+
+   p_current = &sys->array[index_current];
+   v3_copy( co, p_current->co );
+   v3_copy( normal, p_current->normal );
+   p_current->alpha = alpha;
+   v3_zero( p_current->right );
+}
+
+static void trail_system_debug( trail_system *sys ){
+   for( i32 i=0; i<sys->count; i ++ ){
+      i32 i0 = sys->head - sys->count + i;
+      if( i0 < 0 ) i0 += sys->max;
+
+      trail_point *p0 = &sys->array[i0];
+      vg_line_point( p0->co, 0.04f, 0xff000000 | (u32)(p0->alpha*255.0f) );
+      vg_line_arrow( p0->co, p0->right, 0.3f, VG__GREEN );
+
+      if( i == sys->count-1 ) break;
+
+      i32 i1 = i0+1;
+      if( i1 == sys->max ) i1 = 0;
+
+      trail_point *p1 = &sys->array[i1];
+      vg_line( p0->co, p1->co, VG__RED );
+   }
+}
+
+struct trail_init_args {
+   trail_system *sys;
+};
+
+static void async_trail_init( void *payload, u32 size ){
+   struct trail_init_args *args = payload;
+   trail_system *sys = args->sys;
+
+   glGenVertexArrays( 1, &sys->vao );
+   glGenBuffers( 1, &sys->vbo );
+   glBindVertexArray( sys->vao );
+
+   size_t stride = sizeof(trail_vert);
+
+   glBindBuffer( GL_ARRAY_BUFFER, sys->vbo );
+   glBufferData( GL_ARRAY_BUFFER, sys->max*stride*2, NULL, GL_DYNAMIC_DRAW );
+
+   /* 0: coordinates */
+   glVertexAttribPointer( 0, 4, GL_FLOAT, GL_FALSE, stride, (void*)0 );
+   glEnableVertexAttribArray( 0 );
+
+   VG_CHECK_GL_ERR();
+}
+
+static void trail_alloc( trail_system *sys, u32 max ){
+   size_t stride = sizeof(trail_vert);
+   sys->max = max;
+   sys->array = vg_linear_alloc( vg_mem.rtmemory, max*sizeof(trail_point) );
+   sys->vertices = vg_linear_alloc( vg_mem.rtmemory, max*stride*2 );
+
+   vg_async_item *call = vg_async_alloc( sizeof(struct trail_init_args) );
+
+   struct trail_init_args *init = call->payload;
+   init->sys = sys;
+   vg_async_dispatch( call, async_trail_init );
+}
+
+static void trail_system_prerender( trail_system *sys ){
+#if 0
+   glBindVertexArray( sys->vao );
+
+   size_t stride = sizeof(trail_vert);
+   glBindBuffer( GL_ARRAY_BUFFER, sys->vbo );
+   glBufferSubData( GL_ARRAY_BUFFER, 0, sys->alive*stride*4, sys->vertices );
+#endif
+}
+
+static void trail_system_render( trail_system *sys, camera *cam ){
+#if 0
+   glDisable( GL_CULL_FACE );
+   glEnable( GL_DEPTH_TEST );
+
+   shader_trail_use();
+   shader_trail_uPv( cam->mtx.pv );
+   shader_trail_uPvPrev( cam->mtx_prev.pv );
+
+       glBindVertexArray( sys->vao );
+       glDrawElements( GL_TRIANGLES, sys->alive*6, GL_UNSIGNED_SHORT, NULL );
+#endif
+}