纹理映射函数

 

/******************************************************************************* FUNCTION** INPUT** OUTPUT** RETURNS** AUTHOR** DESCRIPTION** Map a point (x, y, z) on a cylinder of radius 1, height 1, that has its axis* of symmetry along the y-axis to the square [0,1]x[0,1].** CHANGES*******************************************************************************/static int cylindrical_image_map(VECTOR EPoint, IMAGE *Image, DBL *u, DBL *v){DBL len, theta;DBL x = EPoint[X];DBL y = EPoint[Y];DBL z = EPoint[Z];if ((Image->Once_Flag) && ((y < 0.0) || (y > 1.0))){return 0;}*v = fmod(y * Image->height, Image->height);/* Make sure this vector is on the unit sphere. */len = sqrt(x * x + y * y + z * z);if (len == 0.0){return 0;}else{x /= len;z /= len;}/* Determine its angle from the point (1, 0, 0) in the x-z plane. */len = sqrt(x * x + z * z);if (len == 0.0){return 0;}else{if (z == 0.0){if (x > 0){theta = 0.0;}else{theta = M_PI;}}else{theta = acos(x / len);if (z < 0.0){theta = TWO_M_PI - theta;}}theta /= TWO_M_PI; /* This will be from 0 to 1 */}*u = (theta * Image->width);return 1;}/******************************************************************************* FUNCTION** INPUT** OUTPUT** RETURNS** AUTHOR** DESCRIPTION** Map a point (x, y, z) on a torus to a 2-d image.** CHANGES*******************************************************************************/static int torus_image_map(VECTOR EPoint, IMAGE *Image, DBL *u, DBL *v){DBL len, phi, theta;DBL r0;DBL x = EPoint[X];DBL y = EPoint[Y];DBL z = EPoint[Z];r0 = Image->Gradient[X];/* Determine its angle from the x-axis. */len = sqrt(x * x + z * z);if (len == 0.0){return 0;}else{if (z == 0.0){if (x > 0){theta = 0.0;}else{theta = M_PI;}}else{theta = acos(x / len);if (z < 0.0){theta = TWO_M_PI - theta;}}}theta = 0.0 - theta;/* Now rotate about the y-axis to get the point (x, y, z) into the x-y plane. */x = len - r0;len = sqrt(x * x + y * y);phi = acos(-x / len);if (y > 0.0){phi = TWO_M_PI - phi;}/* Determine the parametric coordinates. */theta /= TWO_M_PI;phi /= TWO_M_PI;*u = (-theta * Image->width);*v = (phi * Image->height);return 1;}/******************************************************************************* FUNCTION** INPUT** OUTPUT** RETURNS** AUTHOR** DESCRIPTION** Map a point (x, y, z) on a sphere of radius 1 to a 2-d image. (Or is it the* other way around?)** CHANGES*******************************************************************************/static int spherical_image_map(VECTOR EPoint, IMAGE *Image, DBL *u, DBL *v){DBL len, phi, theta;DBL x = EPoint[X];DBL y = EPoint[Y];DBL z = EPoint[Z];/* Make sure this vector is on the unit sphere. */len = sqrt(x * x + y * y + z * z);if (len == 0.0){return 0;}else{x /= len;y /= len;z /= len;}/* Determine its angle from the x-z plane. */phi = 0.5 + asin(y) / M_PI; /* This will be from 0 to 1 *//* Determine its angle from the point (1, 0, 0) in the x-z plane. */len = sqrt(x * x + z * z);if (len == 0.0){/* This point is at one of the poles. Any value of xcoord will be ok... */theta = 0;}else{if (z == 0.0){if (x > 0){theta = 0.0;}else{theta = M_PI;}}else{theta = acos(x / len);if (z < 0.0){theta = TWO_M_PI - theta;}}theta /= TWO_M_PI; /* This will be from 0 to 1 */}*u = (theta * Image->width);*v = (phi * Image->height);return 1;}/** 2-D to 3-D Procedural Texture Mapping of a Bitmapped Image onto an Object:** Simplistic planar method of object image projection devised by DKB and AAC.** 1. Transform texture in 3-D space if requested. 2. Determine local object 2-d* coords from 3-d coords by <X Y Z> triple. 3. Return pixel color value at* that position on the 2-d plane of "Image". 3. Map colour value in Image* [0..255] to a more normal colour range [0..1].*//******************************************************************************* FUNCTION** INPUT** OUTPUT** RETURNS** AUTHOR** DESCRIPTION** Return 0 if there is no color at this point (i.e. invisible), return 1 if a* good mapping is found.** CHANGES*******************************************************************************/static int planar_image_map(VECTOR EPoint, IMAGE *Image, DBL *u, DBL *v){DBL x = EPoint[X];DBL y = EPoint[Y];DBL z = EPoint[Z];if (Image->Gradient[X] != 0.0){if ((Image->Once_Flag) && ((x < 0.0) || (x > 1.0))){return 0;}if (Image->Gradient[X] > 0){*u = fmod(x * Image->width, Image->width);}else{*v = fmod(x * Image->height, Image->height);}}if (Image->Gradient[Y] != 0.0){if ((Image->Once_Flag) && ((y < 0.0) || (y > 1.0))){return 0;}if (Image->Gradient[Y] > 0){*u = fmod(y * Image->width, Image->width);}else{*v = fmod(y * Image->height, Image->height);}}if (Image->Gradient[Z] != 0.0){if ((Image->Once_Flag) && ((z < 0.0) || (z > 1.0))){return 0;}if (Image->Gradient[Z] > 0){*u = fmod(z * Image->width, Image->width);}else{*v = fmod(z * Image->height, Image->height);}}return 1;}

 

PS：这几个函数是在别人的库中抽取出来的，我并没有一一试验，如果有什么问题请及时通知我！