To start, open or build a simple solid model. The bracket from a previous exercise will be used for demonstration purposes.

Transcription

1 Render, Lights, and Shadows The Render programs are techniques using surface shading, surface tones, and surface materials that are then presented in a scene with options for lights and shadows. Modifications to the materials and surfaces can be made for color, smoothness, reflectivity, spectral representation, mirroring as well as other qualities. The objective for this exercise is to gain familiarity with the Render command and dialog areas and to use some of the simple commands in the render option to represent photorealistic models from 3D solid geometry. To start, open or build a simple solid model. The bracket from a previous exercise will be used for demonstration purposes. The standard render default options are not much better than simple shading. The object s color is used to produce shaded surfaces with ambient light. Highlights are few, and the resulting image is unimpressive. It is an image. The viewport displays a bit map (*.bmp) of the rendered scene. A redraw is required to return to the drawing editor. If the object to be rendered is black, change the color. Black does not render well. Use the View-Render-Render command to render this default scene. Accept all defaults. The rendered bitmap will be displayed in the drawing viewport, modeled in the object s color or the object s layer color. Rendering is bland. Only a single ambient light is used in this default setup. Also, the Render-Render type does a poor job of renderening, but is fast. Change the rendering type to Photo real or Photo raytrace for all remaining renderings. A background can be added. The background options are solid color, gradient (in all color variations), image, and merge. Use a gradient of three colors. The colors (Red, Green, Blue) and their intensities can be varied. Use the preview button on the background dialog to view color scheme. Colors should be selected that complement the solid and/or contrast the object against the background.

2 An image can be used as a background. Render recognizes the following image file types: *.bmp, *.png, *.jpg, *.tga, *.tif, *.gif and *.pcx. However, Render produces only the *.bmp file type. Images should be sized for the viewport before importing them to render, else, distortion can result. Render the object with a gradient background. A material can be attached to an object (a solid, face, region etc.) by first selecting(importing) a material from the material library, then, attaching it to an object. The Materials dialog box can call the Materials Library dialog box. Select a material from the Current Library pane on the right, preview the material. Import the material. The material imported is now available to use in a scene. Return to the Materials dialog by pressing OK. Use the attach button to attach the material to an object. Select the object. Each material can be previewed, many material can be loaded into a current drawing. Experiment with a few material types by attaching each to the object and re-rendering. Load the Chrome Blue Sky material. Attach this t o the bracket. Render the scene. (The default render type will not show material detail)

3 Image will show some of the metallic luster of the material. Redraw to return to the drawing editor. A Simple Setting. Often with small objects, renderings look more realistic if the object is presented in a setting, such as sitting on a table or other type of base. For that purpose, use the solid box command to build a table under the object. The table will have a height of about -1 (WCS) For example, from where the bracket is located (0,0,0) draw a box from -2,-2 to 12,10. Use the Material dialog to load a wood material, and attach it to the table. Lights can be added to highlight important features of an object for a rendering. The default lighting, lights all objects in a viewport equally. There are four light types. A point light, spot light, Distant light, and Ambient Light (the latter is the default setting for a distant light) A point light is added by selecting Light from the render pull down menu, or toolbar. Create a new point light. This light must be named. For all other variables, accept the defaults. Position this light using Modify. For the scene shown, Place the light 1 above the object, set the intensity to approximately 30, and set the attenuation to the inverse square setting. Experiment with the three attenuation types.

4 Set up a second Point light, place it in one of the holes of the bracket, or object. Set the intensity to ~5 and the attenuation to the inverse linear option. Point lights emit light in all directions. The intensity is controlled two ways. The light dialog has an intensity slider, similar to a light dimmer. Also, the physical position of the light in the scene will control intensity. The light will attenuate, depending on the option, directly related to the distance between the light and the objects in the scene. This attenuation is true for spot lights as well. The absolute position of the point light can be determined with the show command. The modify command is used to change the position of the light. New light locations can be selected from the viewport (existing objects), or can be placed anywhere in the drawing using the standard move command. Move the location of the point light 3 along the z- axis. The default height for a point light is z=1. Render to view the changes. A light is treated as an object in a drawing but down not render into a scene. Move the lights and render experimenting with distance, intensity and attenuation. Gain familiarity with these commands. Add another point light and place it in front of the object. In a wireframe view, use the move command to position the light directly in front of the object. Render. If the intensity of this light is too great, and creates a hot spot on the object, use the light modify to lower the intensity. Or move the light further away from the object. Add a spot light to the scent. The spot light emits light in one direction. It is used to highlight an important object or feature of a part. The light from the spot light is cone-shaped. There are two conical areas for a spot light. The inner cone is Hot and othe outer cone falls off in intensity away from the center of the cone. The intensities for both the Hotspot and the Fall Off can be varied with a slider control. As with point lights, the intensity of a spot light varies inversely proportional to the distance. To place a spot light, first select a target, then a light location. An absolute coordinate can be used, or a line object or other 2d object can be used to place the light.

5 Add a second spot light to the scene. Vary intensities and render gain some insight into these lights. Play with these lights until you are satisfied with the rendering. Shadows can be represented in the rendering. Rendering with shadows requires more processing time then without. There is a box switch on each light dialog for the use of shadows, and there is a check box on the main render dialog for shadows. This second check box is required to view shadows in a rendering. The others allow individual contro of each light s ability to cast a shadow.

6 The rendering is a pretty picture of a drawing model. It can be saved to disk as a bitmap file. The render dialog contains a destination variable that will write a rendering directly to a file. The default file type is a windows bitmap. The resolution of the rendered file is controlled by a variable on the more options dialog. The default is a *.bmp of 640x480 pixels. Choose a location (folder) for the file and a file name, then render. The rendered file can be used in any number of other computer applications, including word processing, spreadsheets, presentation and software. It can also be re-inserted into a layout in the cad editor. The bitmap is not great for or the web, for that reason, an image editor should be used to convert the bitmap into a *,jpg or *.gif file. These compressed file types are the norm for internet use.