Last active
August 19, 2024 10:24
-
-
Save seobyeongky/78b659accacac2051770ac9ee54dc8d6 to your computer and use it in GitHub Desktop.
Triangle fill algorithm (scanline)
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| public class RenderUtils | |
| { | |
| //Modified From : http://www.sunshine2k.de/coding/java/TriangleRasterization/TriangleRasterization.html | |
| public static void FillTriangleInGrid(Vector2 a, Vector2 b, Vector2 c, System.Action<int,int> plot) | |
| { | |
| /* at first sort the three vertices by y-coordinate ascending so v1 is the topmost vertice */ | |
| if (a.y < b.y) | |
| swap(ref a, ref b); | |
| if (b.y < c.y) | |
| swap(ref b, ref c); | |
| if (a.y < b.y) | |
| swap(ref a, ref b); | |
| /* here we know that v1.y <= v2.y <= v3.y */ | |
| /* check for trivial case of bottom-flat triangle */ | |
| if (b.y == c.y) | |
| { | |
| FillBottomFlatTriangle(a, b, c, plot); | |
| } | |
| /* check for trivial case of top-flat triangle */ | |
| else if (a.y == b.y) | |
| { | |
| FillTopFlatTriangle(a, b, c, plot); | |
| } | |
| else | |
| { | |
| /* general case - split the triangle in a topflat and bottom-flat one */ | |
| Vector2 d = new Vector2((a.x + ((float)(b.y - a.y) / (float)(c.y - a.y)) * (c.x - a.x)), b.y); | |
| FillBottomFlatTriangle(a, b, d, plot); | |
| FillTopFlatTriangle(b, d, c, plot); | |
| } | |
| } | |
| static void FillBottomFlatTriangle(Vector2 v1, Vector2 v2, Vector2 v3, System.Action<int,int> plot) | |
| { | |
| if (IsApproximatelyZero(v1.y - v2.y)) // 예외처리 | |
| return; | |
| if (v2.x > v3.x) | |
| (v2,v3) = (v3,v2); | |
| float invslope1 = (v2.x - v1.x) / (v2.y - v1.y); | |
| float invslope2 = (v3.x - v1.x) / (v3.y - v1.y); | |
| float curx1 = v2.x; | |
| float curx2 = v3.x; | |
| int scanlineYBegin = (int)(v2.y); | |
| float err = v2.y - (scanlineYBegin + 0.5f); | |
| curx1 -= invslope1 * err; | |
| curx2 -= invslope2 * err; | |
| if (err > 0) //예외처리 : 보외법에 의해 삐져나가기 때문에 아예 한 row전체를 skip한다 | |
| { | |
| scanlineYBegin++; | |
| curx1 += invslope1; | |
| curx2 += invslope2; | |
| } | |
| for (int scanlineY = scanlineYBegin; scanlineY < (v1.y + 0.5f); scanlineY++) | |
| { | |
| for (int x = (int)(curx1 + 0.5f); x <= (curx2 - 0.5f); x++) | |
| plot(x, scanlineY); | |
| curx1 += invslope1; | |
| curx2 += invslope2; | |
| } | |
| } | |
| static void FillTopFlatTriangle(Vector2 v1, Vector2 v2, Vector2 v3, System.Action<int,int> plot) | |
| { | |
| if (IsApproximatelyZero(v3.y - v1.y)) // 예외처리 | |
| return; | |
| if (v1.x > v2.x) | |
| (v1,v2) = (v2,v1); | |
| float invslope1 = (v3.x - v1.x) / (v3.y - v1.y); | |
| float invslope2 = (v3.x - v2.x) / (v3.y - v2.y); | |
| float curx1 = v1.x; | |
| float curx2 = v2.x; | |
| int scanlineYBegin = (int)(v1.y); | |
| float err = v1.y - (scanlineYBegin + 0.5f); | |
| curx1 -= invslope1 * err; | |
| curx2 -= invslope2 * err; | |
| if (err < 0) //예외처리 : 보외법에 의해 삐져나가기 때문에 아예 한 row전체를 skip한다 | |
| { | |
| scanlineYBegin--; | |
| curx1 -= invslope1; | |
| curx2 -= invslope2; | |
| } | |
| for (int scanlineY = scanlineYBegin; scanlineY >= (v3.y-0.5f); scanlineY--) | |
| { | |
| for (int x = (int)(curx1 + 0.5f); x <= (curx2 - 0.5f); x++) | |
| plot(x, scanlineY); | |
| // drawLine((int)curx1, scanlineY, (int)curx2, scanlineY); | |
| curx1 -= invslope1; | |
| curx2 -= invslope2; | |
| } | |
| } | |
| static void swap<T>(ref T a, ref T b) | |
| { | |
| (a,b) = (b,a); | |
| } | |
| [MethodImpl(MethodImplOptions.AggressiveInlining)] | |
| static bool IsApproximatelyZero(float f, float eps = 0.001f) | |
| { | |
| // return Mathf.Approximately(f, 0); => 1.49011612E-08도 false로 너무 엄격한 함수 | |
| return -eps <= f && f <= eps; | |
| } | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment