SippRender Command

This command does the rendering of a scene to one or more image stores. The ability to render to multiple image stores allows an application to render to a Tk photo image and save the image in a file at the same time, for example.

The scanning direction determines which types of image stores may be rendered together. Output objects may be written from top to bottom or from bottom to top. File objects are written in only one direction or another, while memory resident objects can be written in either direction. Image stores that are written in opposing directions may not be rendered at the same time. Pixmaps may be used as a buffer to store images that can then be saved to other image stores with conflicting scan-directions.

The image is created with the pixel dimensions xsize by ysize. outputlist is a list of output target handles. The image is written in the Portable Pixel Map (PPM) format unless mode is LINE, in which case it is written in the Portable Bit Map (PBM) format. Mode decides in which mode the image should be rendered and should be one of PHONG, GOURAUD, FLAT or LINE. The integer value oversampling controls how much oversampling should be done for anti-aliasing. Each pixel will be the average of a oversampling by oversampling matrix of subpixels. Oversampling is ignored if mode is LINE.

The following optional flags may be specified:

• -odd - Render old scanlines, useful for creating interlaced movies. (Not allowed for LINE mode).
• -even - Render even scanlines. (Not allowed for LINE mode).
• -both - Render all scan lines. This is the default, only one of -odd, -even or -both may be specified.
• -update period - Specified the updated period when this command is used in a Tk application. This is the frequency at which Tk events, such as button presses, are handled. The approximate unit is the time it takes to render one pixel. Zero disables updates. If not specified, period is the size of one scanline. The processing of pending signals will also occur at this interval, which may be useful in non-Tk based applications.
• -clear - Causes images rendered to Tk photo images to be cleared before rendering the image. This is the default.
• -noclear - Causes images rendered to a Tk photo image to not be cleared before rendering the image. The contents of the previously rendered image will remain until a scanline is overwriten by the new image. This is most useful for overwriting a LINE rendered image with fully rendered image. Only one of -clear or -noclear may be specified.
• -either - Specifies that the image to be rendered either top down or bottom up. If no file image store overrides this specification, then top-down is used. This is the default.
• -topdown - Causes the image to be rendered from the top down. It is useful for specifying if scanlines appear in the a Tk photo image starting at the top. This may not be specified with a bottom-up image store.
• -bottomup - Causes the image to be rendered from the bottom up. It is useful for specifying if scanlines appear in a Tk photo image starting at the bottom. This may not be specified with a bottom-up image store. Only one of -topdown and -bottomup may be specified.