From 85e0098733bc5fa6545590a285f046e668ed5a21 Mon Sep 17 00:00:00 2001
From: hgn <hgodden00@gmail.com>
Date: Tue, 19 Oct 2021 20:55:46 +0100
Subject: [PATCH] accurate path/curve following

---
 fishladder.c  | 75 +++++++++++++++++++++++++++++++++++++++++++++++++--
 vg/vg_lines.h |  8 ++++++
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/fishladder.c b/fishladder.c
index 21fe2ff..bf877e3 100644
--- a/fishladder.c
+++ b/fishladder.c
@@ -1051,7 +1051,7 @@ void vg_render(void)
 	if( world.simulating )
 	{
 		float scaled_time = (vg_time-world.sim_start)*2.0f;
-		float lerp = 1.0f-(scaled_time - (float)world.sim_frame);
+		float lerp = scaled_time - (float)world.sim_frame;
 		
 		v4f dot_colour = { 0.0f, 0.0f, 0.0f, 1.0f };
 		
@@ -1065,7 +1065,78 @@ void vg_render(void)
 			colour_code_v3( fish->payload, dot_colour );
 			glUniform4fv( SHADER_UNIFORM( shader_tile_colour, "uColour" ), 1, dot_colour );
 			
-			glUniform3f( SHADER_UNIFORM( shader_tile_colour, "uOffset" ), (float)fish->pos[0] + 0.5f - (float)fish->dir[0]*lerp, (float)fish->pos[1] + 0.5f - (float)fish->dir[1]*lerp, 0.125f );
+			// Evaluate position
+			struct cell *cell = pcell(fish->pos);
+			v2f fish_pos;
+			
+			v2f const curve_3[] = {{0.5f,1.0f},{0.5f,0.625f},{0.625f,0.5f},{1.0f,0.5f}};
+			v2f const curve_6[] = {{0.5f,1.0f},{0.5f,0.625f},{0.375f,0.5f},{0.0f,0.5f}};
+			v2f const curve_9[] = {{1.0f,0.5f},{0.625f,0.5f},{0.5f,0.375f},{0.5f,0.0f}};
+			v2f const curve_12[]= {{0.0f,0.5f},{0.375f,0.5f},{0.5f,0.375f},{0.5f,0.0f}};
+			
+			v2f const curve_7[] = {{0.5f,0.8438f},{0.875f,0.8438f},{0.625f,0.5f},{1.0f,0.5f}};
+			v2f const curve_7_1[] = {{0.5f,0.8438f},{1.0f-0.875f,0.8438f},{1.0-0.625f,0.5f},{0.0f,0.5f}};
+			
+			float const linear_section = 0.1562f;
+			
+			v2f const *curve;
+			
+			float t = lerp;
+			
+			switch( cell->config )
+			{
+				case 13:
+					if( fish->dir[0] == 1 )
+						curve = curve_12;
+					else
+						curve = curve_9;
+				break;
+				case 3: curve = curve_3; break;
+				case 6: curve = curve_6; break;
+				case 9: curve = curve_9; break;
+				case 12: curve = curve_12; break;
+				case 7:
+					if( t > linear_section )
+					{
+						t -= linear_section;
+						t *= (1.0f/(1.0f-linear_section));
+						
+						curve = cell->state & FLAG_FLIP_FLOP? curve_7: curve_7_1;
+					}
+					else curve = NULL;
+				break;
+				default: curve = NULL; break;
+			}
+			
+			if( curve )
+			{
+				// bezier thing
+				float t2 = t * t;
+				float t3 = t * t * t;
+
+				float cA = 3.0f*t2 - 3.0f*t3;
+				float cB = 3.0f*t3 - 6.0f*t2 + 3.0f*t;
+				float cC = 3.0f*t2 - t3 - 3.0f*t + 1.0f;
+
+				fish_pos[0] = t3*curve[3][0] + cA*curve[2][0] + cB*curve[1][0] + cC*curve[0][0];
+				fish_pos[1] = t3*curve[3][1] + cA*curve[2][1] + cB*curve[1][1] + cC*curve[0][1];
+				fish_pos[0] += (float)fish->pos[0];
+				fish_pos[1] += (float)fish->pos[1];
+			}
+			else
+			{
+				v2f origin;
+				origin[0] = (float)fish->pos[0] + (float)fish->dir[0]*-0.5f + 0.5f;
+				origin[1] = (float)fish->pos[1] + (float)fish->dir[1]*-0.5f + 0.5f;
+				
+				fish_pos[0] = origin[0] + (float)fish->dir[0]*t;
+				fish_pos[1] = origin[1] + (float)fish->dir[1]*t;
+			}
+			
+			vg_line_box( (v2f){fish->pos[0],fish->pos[1]}, 
+			(v2f){ (float)fish->pos[0]+1.0f, (float)fish->pos[1]+1.0f }, 0xffffffff );
+			
+			glUniform3f( SHADER_UNIFORM( shader_tile_colour, "uOffset" ), fish_pos[0], fish_pos[1], 0.125f );
 			draw_mesh( 0, 32 );
 		}
 	}
diff --git a/vg/vg_lines.h b/vg/vg_lines.h
index 469664a..b6f52bd 100644
--- a/vg/vg_lines.h
+++ b/vg/vg_lines.h
@@ -123,3 +123,11 @@ static void vg_line( v2f from, v2f to, u32 colour )
 {
 	vg_line2( from, to, colour, colour );
 }
+
+static void vg_line_box( v2f min, v2f max, u32 colour )
+{
+	vg_line( min, (v2f){min[0],max[1]}, colour );
+	vg_line( (v2f){min[0],max[1]}, max, colour );
+	vg_line( max, (v2f){max[0],min[1]}, colour );
+	vg_line( (v2f){max[0],min[1]}, min, colour );
+}
-- 
2.25.1