再读OpenGL红宝书(1-8章)【续】

电玩女神 2022-02-01 01:45 187阅读 0赞

26）光照模型有4部分：全局环境光，近视点或远视点，双面光照，镜面反射颜色是否和环境颜色，散射颜色分开。要指定全局环境光，可以如下:

GLfloat ambient\[\] = \{0.3,0.3,0.3,1.0\};glLightModelfv(GL\_LIGHT\_MODEL\_AMBIENT,ambient);

顶点的镜面反射亮度取决于该点的法线，顶点相对于光源的方向以及顶点相对于视点的方向。要使用近视点，可以这样：glLightModelfv(GL\_LIGHT\_MODEL\_LOCAL\_VIEWER,GL\_TRUE);这就将视点放置在(0,0,0)处. glLightModelfv(GL\_LIGHT\_MODEL\_TWO\_SIDE,GL\_TRUE)启用双面光照。典型的光照计算中，分别计算环境光，散射光，镜面反射光和发射光的贡献，然后进行叠加，而在这之后进行纹理映射的话，镜面反射区可能被覆盖，为了解决这个问题，可以glLightModelfv(GL\_LIGHT\_MODEL\_COLOR\_CONTROL,GL\_SEPARATE\_SPECULAR\_COLOR); 这样，每个顶点光照计算将产生两种颜色，主颜色和辅助颜色，前者包含所以非镜面反射光照的贡献，后者是所以镜面反射光照的总贡献。纹理映射的时候只将主颜色和纹理颜色混合起来，执行万纹理映射后，再将主颜色和纹理颜色的混合结果与辅助颜色混合起来。

27) 不同材质属性的示例：

200791801.jpg

void init(void)

GLfloat ambient\[\] = \{ 1.0, 0.0, 0.0, 1.0 \};

GLfloat diffuse\[\] = \{ 1.0, 1.0, 1.0, 1.0 \};

GLfloat specular\[\] = \{ 1.0, 1.0, 1.0, 1.0 \};

GLfloat position\[\] = \{ 0.0, 3.0, 2.0, 0.0 \};

GLfloat lmodel\_ambient\[\] = \{ 0.4, 0.4, 0.4, 1.0 \};

GLfloat local\_view\[\] = \{ 0.0 \};

glClearColor(0.0, 0.1, 0.1, 0.0);

glEnable(GL\_DEPTH\_TEST);

glShadeModel(GL\_SMOOTH);

glLightfv(GL\_LIGHT0, GL\_AMBIENT, ambient);

glLightfv(GL\_LIGHT0, GL\_DIFFUSE, diffuse);

glLightfv(GL\_LIGHT0, GL\_POSITION, position);

glLightModelfv(GL\_LIGHT\_MODEL\_AMBIENT, lmodel\_ambient);

glLightModelfv(GL\_LIGHT\_MODEL\_LOCAL\_VIEWER, local\_view);

glEnable(GL\_LIGHTING);

glEnable(GL\_LIGHT0);

void display(void)

GLfloat no\_mat\[\] = \{ 0.0, 0.0, 0.0, 1.0 \};

GLfloat mat\_ambient\[\] = \{ 0.7, 0.7, 0.7, 1.0 \};

GLfloat mat\_ambient\_color\[\] = \{ 0.8, 0.8, 0.2, 1.0 \};

GLfloat mat\_diffuse\[\] = \{ 0.1, 0.5, 0.8, 1.0 \};

GLfloat mat\_specular\[\] = \{ 1.0, 1.0, 1.0, 1.0 \};

GLfloat no\_shininess\[\] = \{ 0.0 \};

GLfloat low\_shininess\[\] = \{ 5.0 \};

GLfloat high\_shininess\[\] = \{ 100.0 \};

GLfloat mat\_emission\[\] = \{0.3, 0.2, 0.2, 0.0\};

glClear(GL\_COLOR\_BUFFER\_BIT | GL\_DEPTH\_BUFFER\_BIT);

/\*  draw sphere in first row, first column

\*  diffuse reflection only; no ambient or specular

\*/

glPushMatrix();

glTranslatef (-3.75, 3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, no\_mat);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in first row, second column

\*  diffuse and specular reflection; low shininess; no ambient

\*/

glPushMatrix();

glTranslatef (-1.25, 3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, no\_mat);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, low\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in first row, third column

\*  diffuse and specular reflection; high shininess; no ambient

\*/

glPushMatrix();

glTranslatef (1.25, 3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, no\_mat);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, high\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in first row, fourth column

\*  diffuse reflection; emission; no ambient or specular reflection

\*/

glPushMatrix();

glTranslatef (3.75, 3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, no\_mat);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, mat\_emission);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in second row, first column

\*  ambient and diffuse reflection; no specular

\*/

glPushMatrix();

glTranslatef (-3.75, 0.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in second row, second column

\*  ambient, diffuse and specular reflection; low shininess

\*/

glPushMatrix();

glTranslatef (-1.25, 0.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, low\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in second row, third column

\*  ambient, diffuse and specular reflection; high shininess

\*/

glPushMatrix();

glTranslatef (1.25, 0.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, high\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in second row, fourth column

\*  ambient and diffuse reflection; emission; no specular

\*/

glPushMatrix();

glTranslatef (3.75, 0.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, mat\_emission);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in third row, first column

\*  colored ambient and diffuse reflection; no specular

\*/

glPushMatrix();

glTranslatef (-3.75, -3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient\_color);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in third row, second column

\*  colored ambient, diffuse and specular reflection; low shininess

\*/

glPushMatrix();

glTranslatef (-1.25, -3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient\_color);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, low\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in third row, third column

\*  colored ambient, diffuse and specular reflection; high shininess

\*/

glPushMatrix();

glTranslatef (1.25, -3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient\_color);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, mat\_specular);

glMaterialfv(GL\_FRONT, GL\_SHININESS, high\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, no\_mat);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

/\*  draw sphere in third row, fourth column

\*  colored ambient and diffuse reflection; emission; no specular

\*/

glPushMatrix();

glTranslatef (3.75, -3.0, 0.0);

glMaterialfv(GL\_FRONT, GL\_AMBIENT, mat\_ambient\_color);

glMaterialfv(GL\_FRONT, GL\_DIFFUSE, mat\_diffuse);

glMaterialfv(GL\_FRONT, GL\_SPECULAR, no\_mat);

glMaterialfv(GL\_FRONT, GL\_SHININESS, no\_shininess);

glMaterialfv(GL\_FRONT, GL\_EMISSION, mat\_emission);

glutSolidSphere(1.0, 16, 16);

glPopMatrix();

glFlush();

28）颜色材质模式，

glColorMaterial(GL\_FRONT, GL\_DIFFUSE);glEnable(GL\_COLOR\_MATERIAL);这将导致正面的DIFFUSE总是设置为当前颜色

29）混合时，首先指定源因子和目标因子，然后按照公式进行混合（默认的操作是相加），设置因子有两种方式：glBlenFunc()和glBlendFuncSeparate()（它可以指定4个因子，即可以使用不同的方式来混合RGB和alpha值）。除了默认的加法外，还可以使用glBlendEquation()来指定其他的混合方式（如减法等）。

30）                启用反走样功能：glEnable(GL\_POINT\_SMOOTH)或glEnable (GL\_LINE\_SMOOTH);glEnable (GL\_BLEND);或者采用glHint（），例如：

glEnable (GL\_LINE\_SMOOTH);

glEnable (GL\_BLEND);

glBlendFunc (GL\_SRC\_ALPHA, GL\_ONE\_MINUS\_SRC\_ALPHA);

glHint (GL\_LINE\_SMOOTH\_HINT, GL\_DONT\_CARE);

31）雾的效果示例：

200791803.jpg

static GLint fogMode;

/\*  Initialize depth buffer, fog, light source,

\*  material property, and lighting model.

\*/

static void init(void)