RenderMan提供了丰富的程序化生成几何体的方法，包括基于外部程序的RIB生成、基于DSO的直接RI接口调用等。我将通过制作一个直接渲染Karakatoa的PRT粒子文件来演示如何制作类似的插件提高制作效率。本文的DSO在VC8 32bit编译器下编译，在RPS 13.5.2以及Aqsis 1.6.0下得到的结果完全相同。下面是一个起步的DSO用来生成3D Sobol序列并显示出来。
Code // PRTRENDER#ifdef WINDOWS #define PRTRENDER extern "C" __declspec( dllexport ) #pragma comment(lib,"prman.lib") #pragma comment(lib,"libgsl.lib")#else #define PRTRENDER extern "C"#endif#include <stdlib.h>#include <stdio.h>#include <string.h>#include <math.h>#include <time.h>#include <ri.h>#include <gsl/gsl_qrng.h>PRTRENDER RtPointer ConvertParameters(RtString ParamStr){ // RtString FilePath = strdup(ParamStr); // fprintf(stdout,"PRTRENDER DSO INFO : Import PRT @ [%s]\n",FilePath); // return (RtPointer)FilePath;}PRTRENDERRtVoid Subdivide(RtPointer Data, RtFloat Detail){ RtInt N = 1024; RtToken VarP = { "P"}; RtToken VarCWidth = { "constantwidth"}; gsl_qrng* QRNG = gsl_qrng_alloc(gsl_qrng_sobol,3); RtFloat* P = (RtFloat*)malloc( sizeof(float)*N*3 ); for( int i=0; i<N; ++i ) { double SingleSobol[3]; gsl_qrng_get(QRNG,SingleSobol); int j = i*3; P[j+0] = SingleSobol[0] * 2.0 - 1.0; P[j+1] = SingleSobol[1] * 2.0 - 1.0; P[j+2] = SingleSobol[2] * 2.0 - 1.0; } RtFloat CWidth = 0.01f; RtToken DataVar[2] = {VarP,VarCWidth}; RtPointer DataPointers[2] = {P,&CWidth}; RiPointsV(N,2,DataVar,DataPointers); free(P); gsl_qrng_free(QRNG);}PRTRENDERRtVoid Free(RtPointer Data){ // free(Data);} 这是在Maya中建模的粒子模型，导出为PRT格式的文件，而后使用DSO读取后直接渲染之。
RenderMan supports to generate procedural primitives dynamically, based on both external stdin/stdout execute or DSO. The first is less efficient because the render has to parse the RIB into RI calls again. I will show you how to use this feature to render Karakatoa particles from an PRT file in RenderMan-like render. This DSO has been tested in RPS 13.5 and Aqsis 1.6. Let's begin from an tiny DSO which generate 3D Sobol quasi-random sequence. We made the particles in Maya, exported it as PRT file, and then rendered it by DSO directly.
