【发布时间】：2020-08-19 13:57:41
【问题描述】：
我有一个 opengl 立方体，我想为所有 6 个面设置纹理。
我需要多个纹理吗？
这是当前立方体的截图：
基本上我不知道如何将纹理包裹在整个立方体周围...
这是我定义 IBO 和 VBO 的 cube.h 头文件
#pragma once
#include <GL\glew.h>
class cube {
public:
cube() {
x = 0;
y = 0;
z = 0;
width = 0;
vertices = 0;
indices = 0;
}
cube(GLfloat X, GLfloat Y, GLfloat Z, float w) {
x = X;
y = Y;
z = Z;
width = w;
vertices = new GLfloat[40];
//1
vertices[0] = x; //x pos
vertices[1] = y; //y pos
vertices[2] = z; //z pos
vertices[3] = 0; //x pos in texture
vertices[4] = 1; //y pos in texture
//2
vertices[5] = x + width;
vertices[6] = y;
vertices[7] = z;
vertices[8] = 1;
vertices[9] = 1;
//3
vertices[10] = x;
vertices[11] = y - width;
vertices[12] = z;
vertices[13] = 0;
vertices[14] = 0;
//4
vertices[15] = x + width;
vertices[16] = y - width;
vertices[17] = z;
vertices[18] = 1;
vertices[19] = 0;
//5
vertices[20] = x;
vertices[21] = y;
vertices[22] = z - width;
vertices[23] = 0;
vertices[24] = 1;
//6
vertices[25] = x + width;
vertices[26] = y;
vertices[27] = z - width;
vertices[28] = 1;
vertices[29] = 1;
//7
vertices[30] = x;
vertices[31] = y - width;
vertices[32] = z - width;
vertices[33] = 0;
vertices[34] = 0;
//8
vertices[35] = x + width;
vertices[36] = y - width;
vertices[37] = z - width;
vertices[38] = 1;
vertices[39] = 0;
//indices
indices = new unsigned int[36];
//0
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
//1
indices[3] = 1;
indices[4] = 2;
indices[5] = 3;
//2
indices[6] = 4;
indices[7] = 5;
indices[8] = 6;
//3
indices[9] = 5;
indices[10] = 6;
indices[11] = 7;
//4
indices[12] = 4;
indices[13] = 0;
indices[14] = 1;
//5
indices[15] = 4;
indices[16] = 5;
indices[17] = 1;
//6
indices[18] = 6;
indices[19] = 2;
indices[20] = 3;
//7
indices[21] = 6;
indices[22] = 7;
indices[23] = 3;
//8
indices[24] = 1;
indices[25] = 5;
indices[26] = 3;
//9
indices[27] = 5;
indices[28] = 7;
indices[29] = 3;
//10
indices[30] = 4;
indices[31] = 0;
indices[32] = 2;
//11
indices[33] = 4;
indices[34] = 6;
indices[35] = 2;
}
GLfloat* vertices;
unsigned int* indices;
private:
GLfloat x;
GLfloat y;
GLfloat z;
float width;
};
这段代码所做的只是为以后使用的多维数据集对象设置一个简单的 VBO 和 IBO/EBO。
【问题讨论】：
-
最简单的方法是复制顶点，因为同一个顶点的每一侧都有不同的纹理坐标......所以你的缓冲区中应该有
6*4*5=120而不是8*5=40。如果您使用所有 6 个面的单一纹理（如剪纸模型）或单面的完整纹理，那么您只需复制纹理坐标在面之间不同的点，从而降低 120 很多。欲了解更多信息，请参阅How do I sort the texture positions based on the texture indices given in a Wavefront (.obj) file? -
另一种选择是使用 2 个索引，一个用于顶点，一个用于 TexCoord，点只有 8*3，纹理只有 4*2 或 6*4*2，但这需要着色器才能工作。
-
@Spektre 你能写出实施中的内容吗？我对你的意思有点困惑......
-
@Jcsq6 您必须为立方体的每一侧指定单独的顶点元组和关联的纹理坐标。你不能使用索引。立方体的 6 个面中的每一个都由 4 个元组和 5 个分量（x、y、z、u、v）组成。另请参阅How do I wrap a sprite around a cube without GL_REPEAT?
-
@Rabbid76 很抱歉，但我似乎还是不明白。我使用的是 (x, y, z u, v) 格式。你是说我不应该使用 IBO？