三角形绘制优化

src/Raster.cc

@@ -163,8 +163,16 @@ void Raster::drawSpan(const Span &span) {
 
     Rgba color;
     float length = span.xEnd - span.xStart;
-    for (int i = span.xStart; i <= span.xEnd; i++) {
-        color = colorLerp(span.color1, span.color2, (float) (i - span.xStart) / length);
+    
+    
+    int startX = tmax<int>(span.xStart, 0);
+    int endX = tmin<int>(span.xEnd, _width);
+    
+    float scale = (startX - span.xStart) / length;
+    
+    //优化3 x轴越界处理
+    for (int i = startX; i <= endX; i++) {
+        color = colorLerp(span.color1, span.color2, (float) (i - startX) / length);
         setPixel(i, span.y, color);
     }
 }
@@ -182,16 +190,20 @@ void Raster::drawEge(const Ege& e1, const Ege& e2) {
     float scale2 = 0;
 
 
-    //优化2 不画三角形坐标y以为的部分
-//    int startY = tmin<int>(e2.y2, _height);
-//    int endY = tmax<int>(e2.y1, 0);
-//    scale2 = (startY - _height) / yOffset2;
+    //优化2 y轴越界处理
+    int startY2 = tmin<int>(e2.y2, _height);
+    int endY2 = tmax<int>(e2.y1, 0);
+    scale2 = (e2.y2 - startY2) / yOffset2;
 
+    int startY1 = tmin<int>(e1.y2, _height);
+    float s = (e1.y2 - startY1) / yOffset1;
+    scale1 = tmax<float>(scale1, s);
 
+    //printf("")
 
     Rgba colorE1;
     Rgba colorE2;
-    for (int y = e2.y2; y > e2.y1; y--) {
+    for (int y = startY2; y > endY2; y--) {
 
         int x2;
         if (e2.x2 < e2.x1) {

src/draw_triangle.cc

@@ -72,17 +72,17 @@ void example3() {
 
 void example4() {
 
-    int2 p[3] = {
-        int2(50, 50),
-        int2(250, 250),
-        int2(300, 150)
-    };
-
-    //            int2 p[3] = {
-    //                int2(100, 150),
-    //                int2(250, 250),
-    //                int2(350, 50)
-    //            };
+//    int2 p[3] = {
+//        int2(-50, 50),
+//        int2(250, 800),
+//        int2(300, 150)
+//    };
+
+                int2 p[3] = {
+                    int2(100, 150),
+                    int2(250, 250),
+                    int2(350, 50)
+                };
 
     Ege e0(p[0].x, p[0].y, p[1].x, p[1].y, Rgba(255, 0, 0, 0), Rgba(0, 255, 0, 0));
     Ege e1(p[1].x, p[1].y, p[2].x, p[2].y, Rgba(0, 255, 0, 0), Rgba(0, 0, 255, 0));