三角形光栅化算法

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "shader_s.h"

#include <iostream>
#include <vector>
using namespace std;
unsigned int VBO, VAO;
vector<float> vertices;
double xpos, ypos;
int n = 0;
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 800;


float f(float x, float y, float x0, float y0, float x1, float y1) {  
	//过（x0，y0）和（x1,y1）的隐式直线方程
	return (y0 - y1) * x + (x1 - x0) * y + x0 * y1 - x1 * y0;
}

float floor(float x1, float x2, float x3) {  //最低点
	float x = min(x1, x2);
	x = min(x, x3);
	return x;
}

float ceiling(float x1, float x2, float x3) {  //最高点
	float x = max(x1, x2);
	x = max(x, x3);
	return x;
}

void processInput(GLFWwindow* window);

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	// make sure the viewport matches the new window dimensions; 
	glViewport(0, 0, width, height);
}

// settings

void swap(int& a, int& b) {
	int t = a;
	a = b;
	b = t;
}

void drawTriangle(float x0, float x1, float x2, float y0, float y1, float y2) {  //画三角形
	float ymin, xmin, ymax, xmax;
	ymin = floor(y0, y1, y2);
	xmin = floor(x0, x1, x2);
	ymax = ceiling(y0, y1, y2);
	xmax = ceiling(x0, x1, x2);
	float i, j, k1, k2, k3, fa, fb, fc, f12, f20, f01;
	for (i = xmin; i <= xmax; i++) {
		for (j = ymin; j <= ymax; j++) {
			fa = f(x0, y0, x1, y1, x2, y2);
			fb = f(x1, y1, x2, y2, x0, y0);
			fc = f(x2, y2, x0, y0, x1, y1);
			f12 = f(-1, -1, x1, y1, x2, y2);
			f20 = f(-1, -1, x2, y2, x0, y0);
			f01 = f(-1, -1, x0, y0, x1, y1);
			k1 = f(i, j, x1, y1, x2, y2) / fa;  //a
			k2 = f(i, j, x2, y2, x0, y0) / fb;  //beita
			k3 = 1 - k1 - k2;                   //y
			if (k1 >= 0 && k2 >= 0 && k3 >= 0) {
				if ((k1 > 0 || fa * f12 > 0) && (k2 > 0 || fb * f20 > 0) && (k3 > 0 || fc * f01 > 0)) 
				{  //处理三角形边上的像素
					vertices.push_back(i);
					vertices.push_back(j);
					vertices.push_back(k1);
					vertices.push_back(k2);
					vertices.push_back(k3);
				}
			}
		}
	}
}


int main()
{
	//           x0    x1   x2   y0  y1    y2
	drawTriangle(100, 340, 340, 240, 240, 480);
	drawTriangle(220, 460, 460, 240, 240, 0);
	drawTriangle(460, 460, 700, 120, 360, 360);
	drawTriangle(340, 580, 340, 360, 360, 600);
	

	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif

	// glfw window creation
	// --------------------
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// glad: load all OpenGL function pointers
	// ---------------------------------------
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}

	// build and compile our shader program
	// ------------------------------------
	Shader ourShader("triangle.vert", "triangle.frag"); // you can name your shader files however you like

	// set up vertex data (and buffer(s)) and configure vertex attributes
	// ------------------------------------------------------------------

	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);
	// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(float) * vertices.size(), &vertices[0], GL_STATIC_DRAW);
	// position attribute
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);
	// color attribute
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(2 * sizeof(float)));
	glEnableVertexAttribArray(1);
	// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
	// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
	// glBindVertexArray(0);


	glm::mat4 proj = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f, 0.1f, 100.0f);

	glm::mat4 model = glm::mat4(1.0f);
	glm::mat4 view = glm::mat4(1.0f);
	// render loop
	// -----------
	while (!glfwWindowShouldClose(window))
	{
		// input
		// -----
		processInput(window);

		// render
		// ------
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// render the triangle
		ourShader.use();


		glm::mat4 proj = glm::ortho(0.0f, 800.0f, 0.0f, 800.0f, 0.1f, 100.0f);

		glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0, 0.0, -10.0));
		glm::mat4 view = glm::mat4(1.0f);

		unsigned int modelLoc = glGetUniformLocation(ourShader.ID, "model");
		unsigned int viewLoc = glGetUniformLocation(ourShader.ID, "view");
		unsigned int projectLoc = glGetUniformLocation(ourShader.ID, "projection");
		// pass them to the shaders (3 different ways)
		glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
		glUniformMatrix4fv(viewLoc, 1, GL_FALSE, &view[0][0]);
		glUniformMatrix4fv(projectLoc, 1, GL_FALSE, glm::value_ptr(proj));
		// note: currently we set the projection matrix each frame, but since the projection matrix rarely changes it's often best practice to set it outside the main loop only once.
	//	ourShader.setMat4("projection", projection);




		glBindVertexArray(VAO);
		glDrawArrays(GL_POINTS, 0, vertices.size() / 5);


		// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
		// -------------------------------------------------------------------------------
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	// optional: de-allocate all resources once they've outlived their purpose:
	// ------------------------------------------------------------------------
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);

	// glfw: terminate, clearing all previously allocated GLFW resources.
	// ------------------------------------------------------------------
	glfwTerminate();
	return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}