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RT Curvature

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Constant Color

The RT Curvature Shader is a fast and robust method of shading surface discontinuity. This type of shading is most useful in enhancing surfacing details, both modeled and that which is added by displacement. The shading can be enhanced further when used to modulate other types of shading effects. The results it produces are similar to a dirt or an accumulation shader that limits shading to recessed (concave) or exposed (convex) areas of a surface, and its really fast! It works by analyzing the surface in screen-space (whats visible to the viewer) recovering the normal information and then building the shading sample off the defined thresholds. This method of calculation is much faster than fully three dimensional solutions and more robust than strictly 2D solutions.

The RT Curvature Shader works by applying the gradient values designated in the Shaders properties. The outside ends of the gradient terminate in the concave and convex areas of the surfaces topology. The degree of its application can be modified with the 'Support Size' and 'Magnitude' controls. For best results, the shader should be applied to surfacers with visible details, plain, smooth surfaces, especially those of the basic primitives offer too little topology changes for interesting shading results. Also, the shader is extremely sensitive to surface normal changes and may reveal the individual polygons, this can be reduced or eliminated by increasing the Subdivision level of the geometry, or by increasing the 'Coefficient Antialiasing' value of the shader.

While Curvature can be used to apply color directly, it will be more often used as a Mask for other shading layers. For information regarding adding and working with Shader Tree Items Layers, please reference the Shader Tree page of the documentation.

Constant PanelLayer--

Enable: Toggles the effect of the layer on and off, duplicating the functionality of toggling visibility in the Shader Tree. When un-checked (disabled), the layer has no effect on the shading of the scene. However, disabled layers are saved with the scene and are persistent across MODO sessions.

Invert: Inverts the RGB values for the layer producing a negative effect.

Blend Mode: Affects blending between different layers of the same effect type, allowing user the ability to stack several layers for different effects. For more on blending, please reference the 'Blend Modes' page of the documentation.

Opacity: Changes the transparency of the current layer. Reducing this values will increasingly reveal lower layers in the shader tree if present, or dim the effect of the layer itself on the surface.

Locator: Most texture layers also have an associated 'Texture Locator' that is automatically created in the 'Item List'. This defines the mapping of the texture (way the texture is applied) to the surface. The 'Locator' option sets that association. Users can choose alternate Locators, however, the need to do so will be very rare; still, there are some possible instances where users may want multiple texture items to share a single Locator.

RT Curvature--

Antialiasing: The 'Antialiasing' is used to multi-sample the curvature shading results, producing a smoother blending between the contours, especially useful for surfaces where the shader tends to highlight the polygons of the underlying geometry. When enabled the Antialiasing is sampled based on the 'Coefficient Antialiasing' setting. When disabled no antialiasing is calculated.

Coeff Antialiasing: The 'Coefficient Antialiasing' option determines the scale of the antialiasing when enabled. Larger values will produce smoother shading results.

Support Size: The 'Support Size' determines the rough scale of the maximum surface features size used to calculate the Curvature shading. This setting should be set the the same approximate scale as the size of the surface details that are desired to highlight.

Magnitude: This is the absolute maximum curvature value used to compute the curvature amount. Larger values will produce sharper contrasts across the shading of opposing surface details, while smaller values will produce smoother, more broad shading.

Edit Gradient : Pressing this button opens a full-sized gradient editor for creation or refinement of the target gradient at a larger size. With a default Gradient View, the target values should be created in between the 0.0 and 1.0, with the 0.0 position terminating on the outer-most convex area attenuating toward the 1.0 position terminating at the inner-most concave areas.

Gradient Value/Color: These are inline mini gradient editors allowing users to define gradient value keys easily without having to leave the basic MODO interface. Much in the same way a keyframe stores transform values for items, gradient keys will store colors or values and softly attenuate between the defined key positions. Keys can be added by MMB+clicking along the gradient and then with the LMB, the key can be dragged up or down adjusting the value at that position. The gradient bar directly underneath provides a visual reference to the values being generated by the gradient itself. In the Color gradient, pressing the color wheel icon will allow precise input of color values using the standard MODO color picker. The left side of the gradient editor terminates on the outer-most convex area attenuating toward the right-hand side of the gradient terminating at the inner-most concave areas.



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