第十二课,assimp模型加载(绘制篇)

首先创建模型渲染管线

Shader ourShader("1.model_loading.vs", "1.model_loading.fs");

vertexShader

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

out vec2 TexCoords;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

void main()
{
    TexCoords = aTexCoords;    
    gl_Position = projection * view * model * vec4(aPos, 1.0);
}

fragmentShader

#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D texture_diffuse1;

void main()
{    
    FragColor = texture(texture_diffuse1, TexCoords);
}

可以看到,该着色器只引入了aPos顶点位置,aNormal法线,aTexCoords纹理坐标.
引入的全局变量有texture_diffuse1漫反射光照,以及变化矩阵。
因此需要对这些全局变量赋值。

全局变量赋值

ourShader.use();
ourShader.setMat4("projection", projection);
ourShader.setMat4("view", view);
model = glm::mat4(1.0f);
model = glm::translate(model, glm::vec3(0.0f, 0.0f, 0.0f)); // translate it down so it's at the center of the scene
model = glm::scale(model, glm::vec3(1.0f, 1.0f, 1.0f));	// it's a bit too big for our scene, so scale it down
ourShader.setMat4("model", model);

绘制

ourModel.Draw(ourShader);

进入函数内部

void Draw(Shader& shader)
{
    for (unsigned int i = 0; i < meshes.size(); i++)
        meshes[i].Draw(shader);
}

对每一个存储在meshes中的Mesh数据进行draw操作

void Draw(Shader& shader)
{
    // bind appropriate textures
    unsigned int diffuseNr = 1;
    unsigned int specularNr = 1;
    unsigned int normalNr = 1;
    unsigned int heightNr = 1;
    for (unsigned int i = 0; i < textures.size(); i++)
    {
        glActiveTexture(GL_TEXTURE0 + i); // active proper texture unit before binding
        // retrieve texture number (the N in diffuse_textureN)
        string number;
        string name = textures[i].type;
        if (name == "texture_diffuse")
            number = std::to_string(diffuseNr++);
        else if (name == "texture_specular")
            number = std::to_string(specularNr++); // transfer unsigned int to stream
        else if (name == "texture_normal")
            number = std::to_string(normalNr++); // transfer unsigned int to stream
        else if (name == "texture_height")
            number = std::to_string(heightNr++); // transfer unsigned int to stream

        // now set the sampler to the correct texture unit
        glUniform1i(glGetUniformLocation(shader.ID, (name + number).c_str()), i);
        // and finally bind the texture
        glBindTexture(GL_TEXTURE_2D, textures[i].id);
    }

    // draw mesh
    glBindVertexArray(VAO);
    glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);

    // always good practice to set everything back to defaults once configured.
    glActiveTexture(GL_TEXTURE0);
}

glActiveTexture(GL_TEXTURE0 + i);激活第i号纹理绑定器
glUniform1i(glGetUniformLocation(shader.ID, (name + number).c_str()), i);
将全局变量中名为 name + number的纹理采样器,绑定到该Shader的第i号绑定器上。
glBindTexture(GL_TEXTURE_2D, textures[i].id);将第i号纹理的id(存储在texture容器中)绑定到当前激活的绑定器上
即,将第i号纹理通过绑定器(GL_TEXTURE0 + i)与Shader中的名为name + number的采样器绑定。

然后glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);

最终效果

添加光照效果后(使用lightShader着色器)
最终效果图

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