纹理滤波

在纹理映射的过程中，如果图元的大小不等于纹理的大小，OpenGL便会对纹理进行缩放以适应图元的尺寸。我们可以通过设置纹理滤镜来决定OpenGL对某个纹理采用的放大、缩小的算法

光源

环境光

因为我们使用的OpenGL 3.x API，使用可编程管线，不使用glLightfv

修改着色器代码

• 颜色=环境光强度（0.5）* 环境光颜色 * 物体本身颜色

static const char *vertexShaderSource =
    "attribute highp vec4 posAttr;\n"
    "attribute lowp vec3 colAttr;\n"
    "varying lowp vec3 col;\n"
    "uniform highp mat4 projection;\n"
    "uniform highp mat4 view;\n"
    "uniform highp mat4 model;\n"
    "attribute vec2 a_texcoord;\n"
    "varying highp vec2 v_texcoord;\n"
    "void main() {\n"
    "   gl_Position = projection * view * model * posAttr;\n"
    "   v_texcoord = a_texcoord;\n"
    "   col = colAttr;\n"
    "}\n";

static const char *fragmentShaderSource =
    "varying lowp vec3 col;\n"
    "uniform sampler2D texture;\n"
    "uniform lowp vec3 ambientColAttr;\n"
    "varying highp vec2 v_texcoord;\n"
    "void main() {\n"
    "   float ambientStrength = 0.5f;\n"
    "   gl_FragColor = vec4(ambientStrength * ambientColAttr * col, 1.0f);\n"
    "}\n";

获取 环境光属性

//环境光属性
m_ambientColAttr = m_program->uniformLocation("ambientColAttr");

绘制时候设置环境光

QVector3D ambient(1.0f, 1.0f, 1.0f);
m_program->setUniformValue(m_ambientColAttr, ambient);

效果

之所以有这样的效果，是因为左上角白色受环境光影响，反射了环境光颜色

• 白色环境光

  
  
  0_1526954839519_f40f63b4-9d0a-46c9-a505-a98451d42c33-image.png

• 红色环境光

  
  
  0_1526954873463_d6a83b40-63bb-4986-8a4f-d5df3a1475a4-image.png

• 绿色环境光

  
  
  0_1526954902270_14818a8e-daf4-4f8c-8563-2c711e200dbf-image.png

• 蓝色环境光

  
  
  0_1526954923358_7a242e55-54fe-4108-9d41-d39813facab2-image.png

点光源-漫反射

修改着色器代码

我们追加了点光源颜色，光源位置，物体的法线（实际具有增幅/衰减光亮的效果）

static const char *vertexShaderSource =
    "attribute highp vec3 posAttr;\n"
    "attribute lowp vec3 colAttr;\n"
    "varying lowp vec3 col;\n"
    "uniform lowp vec3 aNormal;\n"
    "uniform highp mat4 projection;\n"
    "uniform highp mat4 view;\n"
    "uniform highp mat4 model;\n"
    "attribute vec2 a_texcoord;\n"

    "varying highp vec2 v_texcoord;\n"
    "varying vec3 Normal;\n"
    "varying vec3 FragPos;\n"

    "void main() {\n"
    "   gl_Position = projection * view * model * vec4(posAttr, 1.0);\n"
    "   FragPos = vec3(model * vec4(posAttr, 1.0));\n"
    "   v_texcoord = a_texcoord;\n"
    "   Normal = mat3(transpose(inverse(model))) * aNormal;\n"
    "   col = colAttr;\n"
    "}\n";

static const char *fragmentShaderSource =
    "varying lowp vec3 col;\n"
    "uniform sampler2D texture;\n"
    "uniform lowp vec3 ambientColAttr;\n"
    "uniform lowp vec3 lightColAttr;\n"
    "uniform lowp vec3 lightPosAttr;\n"

    "varying highp vec2 v_texcoord;\n"
    "varying vec3 Normal;\n"
    "varying vec3 FragPos;\n"

    "void main() {\n"
    "   vec3 norm = normalize(Normal);\n"
    "   vec3 lightDir = normalize(lightPosAttr - FragPos);\n"
    "   float ambientStrength = 0.1;\n"
    "   float diffuse = max(dot(norm, lightDir), 0.0);\n"
    "   gl_FragColor = vec4((ambientStrength + diffuse) * lightColAttr * col, 1.0);\n"
    "}\n";

获取 点光源属性

//点光源属性
    m_lightColAttr = m_program->uniformLocation("lightColAttr");
    m_lightPosAttr = m_program->uniformLocation("lightPosAttr");
    m_aNormal = m_program->uniformLocation("aNormal");

绘制时候设置点光

//环境光
    QVector3D ambient(1.0f, 1.0f, 1.0f);
    m_program->setUniformValue(m_ambientColAttr, ambient);

    //点光源-漫反射
    QVector3D pointLightCol(1.0f, 1.0f, 1.0f);
    m_program->setUniformValue(m_lightColAttr, pointLightCol);

    QVector3D pointLightPos(2.0f, 0.0f, 2.0f);
    m_program->setUniformValue(m_lightPosAttr, pointLightPos);

    //法线=强度
    QVector3D objNormal(0.0f, 1.0f, 1.0f);
    m_program->setUniformValue(m_aNormal, objNormal);

效果

0_1526965557596_20180522_125850.gif

高光-镜面反射

光源照射到物体然后反射到人的眼睛里时,物体上最亮的那个点就是高光，
所以我们需要知道眼睛（摄像机）的位置，然后根据光的方向，法线求出反射

修改着色器代码

static const char *vertexShaderSource =
    "attribute highp vec3 posAttr;\n"
    "attribute lowp vec3 colAttr;\n"
    "varying lowp vec3 col;\n"
    "uniform lowp vec3 aNormal;\n"
    "uniform highp mat4 projection;\n"
    "uniform highp mat4 view;\n"
    "uniform highp mat4 model;\n"
    "attribute vec2 a_texcoord;\n"

    "varying highp vec2 v_texcoord;\n"
    "varying vec3 Normal;\n"
    "varying vec3 FragPos;\n"

    "void main() {\n"
    "   gl_Position = projection * view * model * vec4(posAttr, 1.0);\n"
    "   FragPos = vec3(model * vec4(posAttr, 1.0));\n"
    "   v_texcoord = a_texcoord;\n"
    "   Normal = mat3(transpose(inverse(model))) * aNormal;\n"
    "   col = colAttr;\n"
    "}\n";

static const char *fragmentShaderSource =
    "varying lowp vec3 col;\n"
    "uniform sampler2D texture;\n"
    "uniform lowp vec3 ambientColAttr;\n"
    "uniform lowp vec3 lightColAttr;\n"
    "uniform lowp vec3 lightPosAttr;\n"
    "uniform lowp vec3 viewPosAttr;\n"

    "varying highp vec2 v_texcoord;\n"
    "varying vec3 Normal;\n"
    "varying vec3 FragPos;\n"

    "void main() {\n"
    //漫反射
    "   vec3 norm = normalize(Normal);\n"
    "   vec3 lightDir = normalize(lightPosAttr - FragPos);\n"
    "   float ambientStrength = 0.1;\n"
    "   float diffuse = max(dot(norm, lightDir), 0.0);\n"

    //高光
    "   vec3 viewDir = normalize(viewPosAttr - FragPos);\n"
    "   vec3 reflecDir = reflect(-lightDir, norm);\n"
    "   float specularStrength = 0.5;\n"
    "   float specular = pow(max(dot(viewDir, reflecDir), 0.0), 64) * specularStrength;\n"
    "   gl_FragColor = vec4((ambientStrength + diffuse + specular) * lightColAttr * col, 1.0);\n"
    "}\n";

获取 视点属性

//视点属性
    m_viewPosAttr = m_program->uniformLocation("viewPosAttr");

绘制时候设置视点

//视点为摄像机位置
    m_program->setUniformValue(m_viewPosAttr, camera);

效果

仔细看，有高光

0_1526968253241_20180522_134903.gif

源代码

https://gitee.com/chen227/opengl_OpenGLFunctions7