From 2869f5ccdd697c3603a76ca8c6585dd1330b8adb Mon Sep 17 00:00:00 2001
From: InventorXtreme <inventorxtreme@gmail.com>
Date: Mon, 11 Mar 2024 23:27:00 -0400
Subject: [PATCH] actually use optomizaiton on both types of tris

---
 c3d.c | 57 ++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 21 deletions(-)

diff --git a/c3d.c b/c3d.c
index f5c58d1..d95ea90 100644
--- a/c3d.c
+++ b/c3d.c
@@ -30,6 +30,23 @@ float proj; // HALFWIDTH / tan(half_fov) Inited later
 
 bool printdebug;
 
+float Sign(Vector2 *v1, Vector2 *v2, Vector2 *v3) {
+    return (v1->x - v3->x) * (v2->y - v3->y) - (v2->x - v3->x) * (v1->y - v3->y);
+}
+
+static inline bool IsInTri(Tri2D tri, Vector2 p) {
+    float d1, d2, d3;
+    bool has_neg, has_pos;
+
+    d1 = Sign(&p, &tri.a, &tri.b);
+    d2 = Sign(&p, &tri.b, &tri.c);
+    d3 = Sign(&p, &tri.c, &tri.a);
+
+    has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0);
+    has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0);
+
+    return !(has_neg && has_pos);
+}
 static inline Vector3 Tri2DBaryAtPoint(Tri2D *t, Vector2 p) {
     Vector3 retvec;
     Vector2 v0 = Vector2Subtract(t->b, t->a); // cachable
@@ -123,14 +140,27 @@ void FillTopFlatZbuffer(Zee *zee, Tri2D *t, Tri2D *tp) {
 
     for (int scanline = t->c.y; scanline >= t->a.y; scanline--) {
         if (0 <= scanline && scanline < RENDERHEIGHT) {
+
+            Vector3 f1baryatpoint = Tri2DBaryAtPoint(tp, (Vector2){Max(curx1, 0), scanline});
+            float f1depth = DepthAtBary(tp, f1baryatpoint);
+
+            Vector3 f1baryatpoint2 = Tri2DBaryAtPoint(tp, (Vector2){Max(curx1, 0) + 1, scanline});
+            float f1depth2 = DepthAtBary(tp, f1baryatpoint2);
+            float dslope = f1depth2 - f1depth;
+
             for (int i = Max(curx1, 0); i < Min(curx2, RENDERWIDTH); i++) {
                 /* zee[IndexOfZBuff(i, scanline)].triangle = tp; */
 
-                Vector3 baryatpoint = Tri2DBaryAtPoint(tp, (Vector2){i, scanline});
-                float depth = DepthAtBary(tp, baryatpoint);
-                if (depth > zee[IndexOfZBuff(i, scanline)].depth) {
+                /* Vector3 baryatpoint = Tri2DBaryAtPoint(tp, (Vector2){i, scanline}); */
+                /* float depth = DepthAtBary(tp, baryatpoint); */
+
+				
+
+                float aproxdepth = f1depth + (dslope * ((float)i - (float)(Max(curx1, 0))));
+
+                if (aproxdepth > zee[IndexOfZBuff(i, scanline)].depth) {
                     zee[IndexOfZBuff(i, scanline)].triangle = tp;
-                    zee[IndexOfZBuff(i, scanline)].depth = depth;
+                    zee[IndexOfZBuff(i, scanline)].depth = aproxdepth;
                     // printf("here\n");
                 }
             }
@@ -182,6 +212,8 @@ void FillBottomFlatZbuffer(Zee *zee, Tri2D *t, Tri2D *tp) {
                 /* Vector3 baryatpoint = Tri2DBaryAtPoint(tp, (Vector2){i, scanline}); */
                 /* float depth = DepthAtBary(tp, baryatpoint); */
 
+				
+
                 float aproxdepth = f1depth + (dslope * ((float)i - (float)(Max(curx1, 0))));
 
                 if (aproxdepth > zee[IndexOfZBuff(i, scanline)].depth) {
@@ -231,23 +263,6 @@ void DrawTriZuff(Zee *zbuf, Tri2D *t) {
     }
 }
 
-float Sign(Vector2 *v1, Vector2 *v2, Vector2 *v3) {
-    return (v1->x - v3->x) * (v2->y - v3->y) - (v2->x - v3->x) * (v1->y - v3->y);
-}
-
-static inline bool IsInTri(Tri2D tri, Vector2 p) {
-    float d1, d2, d3;
-    bool has_neg, has_pos;
-
-    d1 = Sign(&p, &tri.a, &tri.b);
-    d2 = Sign(&p, &tri.b, &tri.c);
-    d3 = Sign(&p, &tri.c, &tri.a);
-
-    has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0);
-    has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0);
-
-    return !(has_neg && has_pos);
-}
 
 void CtrlLocalCam(LocalCam *cam, float time) {
     cam->velocity.x = 0;