三角形三个顶点的颜色分别为红绿蓝,使用有效边表算法填充三角形
时间: 2024-05-02 13:16:58 浏览: 21
有效边表算法(ETB)是一种扫描线填充算法。以下是使用有效边表算法填充三角形的步骤:
1. 确定三角形的三个顶点的坐标,以及每个顶点的颜色。
2. 对三个顶点按照 y 坐标从小到大进行排序。
3. 针对每个边,计算出斜率倒数 m 和 y 轴截距 b。
4. 对于每一行扫描线,从有效边表中删除所有 yMax = y 的边,将 yMin = y 的边插入有效边表。
5. 对于每个被插入的边,按照 x 坐标从小到大进行排序。
6. 对于每个相邻的边对 (A, B),使用 Bresenham 算法在两条边之间绘制水平线段,并填充指定颜色。
7. 重复步骤 4-6,直到扫描线扫描到三角形的最低点。
以下是一个实现该算法的示例代码(使用 Python 语言):
```python
class Vertex:
def __init__(self, x, y, color):
self.x = x
self.y = y
self.color = color
class Edge:
def __init__(self, vertex1, vertex2):
if vertex1.y < vertex2.y:
self.yMin = vertex1.y
self.yMax = vertex2.y
self.x = vertex1.x
self.color = vertex1.color
else:
self.yMin = vertex2.y
self.yMax = vertex1.y
self.x = vertex2.x
self.color = vertex2.color
self.m = (vertex2.x - vertex1.x) / (vertex2.y - vertex1.y)
self.b = vertex1.x - self.m * vertex1.y
def fillTriangle(vertices):
# Step 1: Sort vertices by y coordinate
vertices.sort(key=lambda v: v.y)
# Step 2: Initialize edge table and active edge table
edgeTable = [[] for i in range(len(vertices))]
activeEdgeTable = []
# Step 3: Fill edge table
for i in range(len(vertices)):
j = (i + 1) % len(vertices)
edge = Edge(vertices[i], vertices[j])
edgeTable[edge.yMin].append(edge)
# Step 4: Scanline fill
for y in range(vertices[0].y, vertices[2].y + 1):
# Remove edges from active edge table
activeEdgeTable = [edge for edge in activeEdgeTable if edge.yMax != y]
# Add edges to active edge table
activeEdgeTable += edgeTable[y]
# Sort active edge table by x coordinate
activeEdgeTable.sort(key=lambda edge: edge.x)
# Fill between edges in active edge table
for i in range(0, len(activeEdgeTable), 2):
edge1 = activeEdgeTable[i]
edge2 = activeEdgeTable[i + 1]
for x in range(int(edge1.x), int(edge2.x) + 1):
color = interpolateColor(edge1.color, edge2.color, (x - edge1.x) / (edge2.x - edge1.x))
drawPixel(x, y, color)
# Update x coordinate of edges in active edge table
for edge in activeEdgeTable:
edge.x += edge.m
def interpolateColor(color1, color2, t):
r = int(color1[0] + t * (color2[0] - color1[0]))
g = int(color1[1] + t * (color2[1] - color1[1]))
b = int(color1[2] + t * (color2[2] - color1[2]))
return (r, g, b)
def drawPixel(x, y, color):
# Placeholder function to draw pixel with color
pass
# Example usage
vertices = [
Vertex(100, 50, (255, 0, 0)), # Red vertex
Vertex(150, 200, (0, 255, 0)), # Green vertex
Vertex(50, 150, (0, 0, 255)) # Blue vertex
]
fillTriangle(vertices)
```