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File List | 1992-07-27 | 20.6 KB | 567 lines

SCN2SFF(1G) NAME scn2sff - format conversion program SYNOPSIS scn2sff [options] {SCNfile|-} [>SFFfile] AUTHOR Antonio Costa, INESC-Norte, 1991 1992 DESCRIPTION _s_c_n_2_s_f_f command performs conversion between a text format (SCN) suitable for scene descriptions to another more simple text format (SFF) that is accepted by the _r_t_r_a_c_e ray-tracer program. The SCN text file describes objects, lights, sur- face definitions, textures, etc. The scene format is described bellow. OPTIONS [C] The parameter _C tells the program to preprocess the input file through the UNIX standard preprocessor (/usr/lib/cpp with option -P). [M] The parameter _M tells the program to preprocess the input file through the M4 preprocessor (/usr/bin/m4). [P"_p_r_e_p_r_o_c_e_s_s_o_r _c_o_m_m_a_n_d"] The parameter _P tells the program to preprocess the input file through the command described (for example, P"/usr/lib/cpp -P -Dabc"). RESTRICTIONS None for the moment. BUGS No bugs known. They have to be hidden deep somewhere, as usual. DESCRIPTION Comments start with % ; or # characters and continue to the end of the line (so there are no nested comments). The commands are processed from the start of the scene, and some have a global effect until they are changed or the scene is complete. Such commands are _r_e_f_r_a_c_t_i_o_n, _s_u_r_f_a_c_e, _t_r_a_n_s_f_o_r_m_a_t_i_o_n_s and _t_e_x_t_u_r_e_s; as commands can be nested by grouping, any command defined inside a group is removed when that group is finished. Example: surface matte white % current surface is matte white refraction 1.1 % current refraction index transform rotate x 15 % transformation group % start of a group of commands surface matte red % new current surface transform scale 2 % transformation sphere 0 0 0 1 % sphere object ungroup % end of group % back to matte white surface, refraction 1.1 % scale transformation is removed ENTITIES The main entities are: _i_n_t_e_g_e_r - it can be a simple number, an integer expression enclosed in parenthesis or the _i_n_t function applied to any real expression. _r_e_a_l - a number, a function or an expression enclosed in parenthesis. _c_o_l_o_r - a triplet of RGB real values between 0 and 1 (in certain cases, it is allowed to be greater than 1 or nega- tive; called _c_o_l_o_r__e_x_t_e_n_d_e_d) or a name (like _r_e_d, _b_l_u_e, etc). _p_o_i_n_t - a triplet of XYZ values (numbers, functions or expressions). _v_e_c_t_o_r - similar to point, but the 3 components cannot be simultaneously equal to 0. _f_i_l_e_n_a_m_e - a set of characters with no blanks between. _e_x_p_r_e_s_s_i_o_n - anything enclosed in parenthesis. Operators are +, -, *, /, ^ (exponentiation) and | (remainder). _f_u_n_c_t_i_o_n - there are many functions available: _i_n_t _s_i_n _c_o_s _t_a_n _a_s_i_n _a_c_o_s _a_t_a_n _s_q_r_t _r_t_o_d _d_t_o_r _e_x_p _l_o_g _a_b_s _m_a_x _m_i_n. There also some functions that operate with vectors and return a number (_d_o_t_v_e_c_t_o_r) and some that return a vector or point (_n_o_r_m_v_e_c_t_o_r _a_d_d_v_e_c_t_o_r _d_i_f_f_v_e_c_t_o_r _s_c_a_l_e_v_e_c_t_o_r _c_r_o_s_s_v_e_c_t_o_r). There is also an operator _m_o_n_o that converts from a value to 3 identical values (good for specifying monochromatic colors). GENERAL COMMANDS The main commands are: _e_y_e (_f_r_o_m) point - default {5,0,0}. _l_o_o_k (_a_t) point - default {0,0,0}. _u_p vector - default {0,1,0}. _a_n_g_l_e (_f_o_v) horizontal [vertical] - half aperture view in degrees (default 22.5 degrees). _b_a_c_k_g_r_o_u_n_d color - the color of the background, at infinite distance (default light_sky_blue). _a_m_b_i_e_n_t color - the diffuse light that illuminates the whole scene (default is {0.1,0.1,0.1}). _r_e_f_r_a_c_t_i_o_n (_i_o_r) index - default is 1. _g_r_o_u_p ... _u_n_g_r_o_u_p - anything enclosed is only defined inside the block, ie, it does not apply outside. LIGHT COMMANDS The commands for definition of light sources are: _l_i_g_h_t _p_o_i_n_t point [color_extended] - default color for lights is white. _l_i_g_h_t _d_i_r_e_c_t_i_o_n_a_l vector [color]. _l_i_g_h_t _s_p_o_t point vector color_extended [angle [factor]] - the light illuminates inside a cone defined by the angle (default 45 degrees) and the transition can be sharp if fac- tor is near 1 or smooth if factor >> 1 (default 1). _l_i_g_h_t _e_x_t_e_n_d_e_d point color_extended radius samples - a spherical light (it is sampled by samples^2 rays). SURFACE COMMANDS The commands for definition of surfaces are: _s_u_r_f_a_c_e color [diffusion specularity phong metalness [tran- sparency]] - phong and metalness are values, the others are colors (defaults {0.9,0.9,0.9} {0.1,0.1,0.1} 3 0 {0.1,0.1,0.1} or transparency only {0,0,0}). _s_u_r_f_a_c_e _s_t_r_a_u_s_s color smoothness metalness [transparency] - all colors (default transparency is {0,0,0}). _s_u_r_f_a_c_e _m_a_t_t_e color - all diffuse surface. _s_u_r_f_a_c_e _p_l_a_s_t_i_c color smoothness phong - surface with big diffusion, small specularity and small phong factor. _s_u_r_f_a_c_e _m_e_t_a_l color smoothness phong - surface with small diffusion, big specularity, big phong factor and metalness factor equal to 1. _s_u_r_f_a_c_e _d_i_e_l_e_c_t_r_i_c color transparency refraction - tran- sparent surface with no diffusion, some specularity, large phong factor and null metalness. _s_u_r_f_a_c_e _g_l_a_s_s color transparency - transparent surface with refraction index equal to 1.52, approximately. OBJECT COMMANDS The commands for objects are of the form _o_b_j_e_c_t object_data or else with local commands that apply only to itself of the form _o_b_j_e_c_t [attributes ... _d_a_t_a] object_data. _s_p_h_e_r_e center radius. _b_o_x center sizes - this is an axis-aligned box. _c_u_b_e center size - again it is axis-aligned. _c_o_n_e apex base base_radius - closed cone. _c_o_n_e _o_p_e_n apex base base_radius. _c_y_l_i_n_d_e_r apex base radius - closed cylinder. _c_y_l_i_n_d_e_r _o_p_e_n apex base radius. _c_o_n_e _t_r_u_n_c_a_t_e_d apex apex_radius base base_radius - closed. _c_o_n_e _t_r_u_n_c_a_t_e_d _o_p_e_n apex apex_radius base base_radius. _w_e_d_g_e point point point depth - defined by a triangular face and depth (face is defined counterclockwise so that depth is measured in the opposite direction of Rigth Hand Rule thumb; this convention also applies to other objects). _t_e_t_r_a point point point point. _p_r_i_s_m depth number_vertices point ... point - closed prism. _p_r_i_s_m _o_p_e_n depth number_vertices point ... point. _p_y_r_a_m_i_d depth number_vertices point ... point - closed pyramid. _p_y_r_a_m_i_d _o_p_e_n depth number_vertices point ... point. _p_y_r_a_m_i_d _t_r_u_n_c_a_t_e_d _o_p_e_n depth apex_scale number_vertices point ... point - it is an open pyramid with the apex scaled by apex_scale in relation to its base (if 0 it is an open pyramid, if 1 it is a prism). _d_i_s_c center normal radius. _r_i_n_g center normal outer_radius inner_radius. _p_a_t_c_h point ... point (12) - a bicubic patch is defined by its corners and 8 exterior points, arranged in this manner: 11 12 7 8 9 10 3 4 5 6 1 2 Normal points according to Right Hand Rule using corners 4- 5-9-8. _p_a_t_c_h _f_i_l_e [point [point]] filename - a group of patches stored in a file; first point is a translation and second is a scale. _p_o_l_y_g_o_n number_vertices point ... point - a polygon (can be concave, but does not have holes). _p_o_l_y_g_o_n _f_i_l_e [point [point]] filename - a group of polygons stored in a file; first point is a translation and second is a scale. _t_r_i_a_n_g_l_e point point point. _q_u_a_d_r_a_n_g_l_e point point point point. _t_r_i_a_n_g_l_e _n_o_r_m_a_l point vector point vector point vector - a triangle with normals in its vertices. _t_r_i_a_n_g_l_e _n_o_r_m_a_l _f_i_l_e point point filename - a group of tri- angles with normals in the vertices stored in a file; first point is a translation and second is a scale. _t_o_r_u_s outer_radius section_radius start_angle end_angle [outer_samples section_samples] - A closed torus is centered in {0,0,0} and lies in the XZ plane. 0 degrees is in the X direction and the angle increases counterclockwise. _t_o_r_u_s _o_p_e_n outer_radius section_radius start_angle end_angle [outer_samples section_samples] - An open torus. _t_e_x_t_3_d _f_i_l_e filename - a group of text primitives stored in a file; each primitive is described by lines and arcs and is extruded (similar to a prism, in a certain way). _c_s_g begin - start of a CSG primitive, ie, left component. _c_s_g next - right component of a CSG primitive. _c_s_g end - end of a CSG primitive. _l_i_s_t begin - start of a list primitive (no nesting allowed). _l_i_s_t end - end of a list primitive. TRANSFORMATION COMMANDS A transformation may be defined globaly or inside a block, and it is post-concatenated with previous transformations. If inside a block, when the block is terminated the transformations defined inside it are removed. Also, when a transformation is an attribute of an object or texture it only exists for that entity. _t_r_a_n_s_f_o_r_m _n_o_n_e - removes all transformations. _t_r_a_n_s_f_o_r_m _s_c_a_l_e factor [factor factor]. _t_r_a_n_s_f_o_r_m _t_r_a_n_s_l_a_t_e point. _t_r_a_n_s_f_o_r_m _r_o_t_a_t_e _x angle. _t_r_a_n_s_f_o_r_m _r_o_t_a_t_e _y angle. _t_r_a_n_s_f_o_r_m _r_o_t_a_t_e _z angle. _t_r_a_n_s_f_o_r_m _r_o_t_a_t_e axis angle. _t_r_a_n_s_f_o_r_m _g_e_n_e_r_a_l point point point [point]. TEXTURE COMMANDS A texture is basically a modification of the surface charac- teristics of an object, a modification of the normal vector in the intersection point or the modification of the inter- section point itself. It is possible to apply transforma- tions to textures, and even keep them independent from the object transformations. _t_e_x_t_u_r_e _n_o_n_e - remove all defined textures. _t_e_x_t_u_r_e _s_c_a_l_e factor [factor factor]. _t_e_x_t_u_r_e _t_r_a_n_s_l_a_t_e point. _t_e_x_t_u_r_e _r_o_t_a_t_e _x angle. _t_e_x_t_u_r_e _r_o_t_a_t_e _y angle. _t_e_x_t_u_r_e _r_o_t_a_t_e _z angle. _t_e_x_t_u_r_e _r_o_t_a_t_e axis angle. _t_e_x_t_u_r_e _g_e_n_e_r_a_l point point point [point]. _t_e_x_t_u_r_e _l_o_c_a_l - generate all the transformations necessary to access the object directly, without considering any object transformations previously defined. _c_h_e_c_k_e_r_s surface [transform] - a chessboard-like pattern of the current surface and the defined surface. _b_l_o_t_c_h scale surface [filename] [transform] - A spray-like mixture of 2 surfaces (the current and the defined). The scale controls the mixture. If a filename is given, it is interpreted as a color palette, and it must contain 256 tri- plets of RGB values in the range 0 to 255 (this format is equal for all the textures that have a _f_i_l_e_n_a_m_e parameter, except _i_m_a_g_e_m_a_p). _b_u_m_p scale [transform] - A normal-modifying texture. _m_a_r_b_l_e [filename] [transform] - A marble-like texture. _f_b_m offset scale omega lambda threshold octaves [filename] [transform] - A fractal brownian motion texture that changes diffusion and specularity. _f_b_m_b_u_m_p offset scale lambda octaves [transform] - a texture that modifies the normal. _w_o_o_d color [transform] - A texture imitating wood (default color is _b_r_o_w_n). _r_o_u_n_d scale [transform] - strange texture that modifies dif- fusion and specularity. _b_o_z_o turbulence [filename] [transform]. _r_i_p_p_l_e_s frequency phase scale [transform] - a texture that imitates ripples (small sinusoidal perturbations of the sur- face). _w_a_v_e_s frequency phase scale [transform] - a texture like waves (multi-interfering sinusoidal perturbations of the surface). _s_p_o_t_t_e_d [filename] [transform] - small color spots. _d_e_n_t_s scale [transform] - small modifications of normal that imitate dents. _a_g_a_t_e [filename] [transform]. _w_r_i_n_k_l_e_s [transform] - a texture that modifies normal imi- tating wrinkles. _g_r_a_n_i_t_e [filename] [transform]. _g_r_a_d_i_e_n_t turbulence direction [filename] [transform] - This texture produces a variation of color following direction given. _i_m_a_g_e_m_a_p turbulence mode u_axis v_axis filename [transform] - An image-mapping texture. Mode parameter controls tiling of texture (0-yes, nonzero-no). The u_axis and v_axis specify the internal texture axis from the 3D axis (1-X, 2- Y, 3-Z). A filename must be given, because it is the image that will be drawn on the surface (the format of the image is the _r_t_r_a_c_e format PIC). _g_l_o_s_s scale [transform] - Glossy-like texture that changes diffusion, specularity and phong factor. _b_u_m_p_3 scale size [transform] - A normal-modifying texture. Changes intersection point, so may produce strange results! EXAMPLES Here are some simple examples: %%%%% example 1 % light source light point 4 3 1 % surface surface matte red sphere 0 0 0 1 % another surface (replaces previous) surface plastic blue mono 0.3 0.3 sphere 3 -0.4 0.4 0.2 % another surface surface plastic yellow mono 0.9 0.9 % transformations for next object(s) transform rotate y rtod(atan(1)) transform translate 3 -0.4 -0.4 box 0 0 0 0.1 0.1 0.3 % remove previous transformation(s) transform none % another surface surface green mono 0.8 mono 0.2 10 0.3 cone 3 0.1 0 3 -0.4 0 0.2 surface matte white csg subtraction begin sphere 0 0 0 1 csg next box 0 0 0 1.1 0.4 0.4 csg end This example is correct, although it does not take full usage of SCN, ie, the capability of defining locally the attributes. It could be rewritten: %%%%% example 2 % light source light point 4 3 1 % now all objects have local attributes sphere surface matte red data 0 0 0 1 sphere surface plastic blue mono 0.3 0.3 data 3 -0.4 0.4 0.2 box surface plastic yellow mono 0.9 0.9 % local transformations transform rotate y rtod(atan(1)) transform translate 3 -0.4 -0.4 % this object is defined in a local coords system % the translation puts it in the right place data 0 0 0 0.1 0.1 0.3 cone surface green mono 0.8 mono 0.2 10 0.3 data 3 0.1 0 3 -0.4 0 0.2 csg subtraction surface matte white data begin sphere 0 0 0 1 csg next box 0 0 0 1.1 0.4 0.4 csg end To produce an image from any of these examples, the example should be stored in a file (suppose _e_x_a_m_p_l_e._s_c_n) and then execute scn2sff example.scn|rtrace w512 p2 A0.1 - example.pic to create the image. If the SCN file contained any _c_p_p preprocessor directives, then scn2sff C example.scn|rtrace w512 p2 A0.1 - example.pic would do. A complete demo example follows: [Start] % example to be traced with parameters like % w512 p2 A0.1 t1 I1 - good quality % or then % w512 p3 A.05 t1 I1 j1 - very good quality %%%%% start eye 5 2 2 fov 20 background light_sky_blue ambient mono 0.2 % dark grey light point 3 5 4 white surface matte red % default surface %%%%% a simple CSG example csg subtraction begin % no attributes for this CSG, so it uses the attributes % of its nodes... % left node csg subtraction % attributes of this CSG object surface matte white texture scale 0.2 checkers surface matte mono 0.3 translate 0.1 0.1 0.1 data begin box 0 0 0 1 1 1 csg next box 0 0 0 1.01 0.5 0.5 list begin % a cylinder must be enclosed in a list, because it is % not a closed object, but 3 objects joined together cylinder 0 1.01 0 0 -1.01 0 0.5 list end csg end csg next % right node sphere 1 1 1 0.5 % default surface assumed sphere 1 1 -1 0.5 sphere surface matte blue data 1 -1 1 0.5 sphere surface matte blue data 1 -1 -1 0.5 csg end %%%%% some 3D text text3d file surface matte yellow data csg.t3d % data is in file %%%%% end [End] The csg.t3d file contents could be: [Start] SPACING 0.1 ORIENTATION 0 0 -1 0 1 0 1 0 0 ENCODING abc.ppe FONT zurichcg.ppf SCALE 0.4 0.4 0.2 AT 1.25 1.5 1.6 "Antonio Costa" FONT renfrew.ppf SCALE 0.4 0.4 0.1 AT 1.1 -0.85 1.1 "/copyright/1992" AT 1.1 -1.3 1.1 "INESCn" # there must be an empty line in the end Description: SPACING is letter spacing ORIENTATION defines how the text appears - 1st: text direction vector (left to right) - 2nd: vertical vector - 3rd: depth vector ENCODING associates logical character names to glyph numbers FONT is the file where the 2D glyphs are defined SCALE controls scaling along ORIENTATION vectors AT is baseline lower left position of text plus text (quoted) [End] HISTORY Copyright (C) 1991 1992 by Antonio Costa. Permission is granted to use this file in whole or in part for any purpose, educational, recreational or commercial, provided that this copyright notice is retained unchanged. This software is available to all free of charge by anonymous FTP. 23-Jul-92 Antonio Costa at INESC-Norte Release 1.3.1 acc@asterix.inescn.pt acc@basinger.inescn.pt