Grass shader for DAZ Studio

Contents

A grassy hill and 3d grass shader text. Introduction Important Concepts Quick Start Quick Tips Parameter Settings Known Issues

Introduction

A dark elf leaps from a grassy hill and surprises a horseman.

The AoA Grass Shader allows 3d grass to be easily applied to any surface. Many controls are available to adjust effects such as blade thickness, grass length, colors and clumping.

The shader is almost entirely procedural so it can be used on any surface, even non-UV-mapped objects.

Because the shader actually creates grass geometry it can be used for scenes where texture based grass would not be suitable due to insufficient closeup detail or noticeable texture tiling. Please note that this extra detail comes at a cost and may render more slowly than a standard, texture-mapped surface.

Important Concepts

A render of a woman sitting on the grass near a stone pathway.

The grass is generated using mathematical formulas and displacement. The shader may be able to generate grass which is extremely fine and tends to look better in large renders and when using fine shading rates (in the DS render settings) such as 0.5 to 0.1.

The shader can be used directly on any surface but, due to clumping, parts of the object may have small areas where little or no grass is seen. This may cause some of the backdrop to be visible through thin spots in the grass.

A technique which corrects this issue and also adds realism, is to use a dirt colored shader on your terrain surface then create a geometry shell of it and apply the grass shader to the geometry shell. This causes your terrain to have two layers, one for dirt and another just slightly above with the grass. This way dirt will show anywhere there are thin spots in the grass just like real life.

This method can also be used along with a simple black and white map to create grass only in certain areas of an object. Simply load an item with dirt, cobblestones or whatever you desire to show in areas where there is no grass, create a geometry shell then apply a grass preset to the shell. Now you can use a black and white texture in the Displacement Mask channel. In areas where the map is white the grass will appear. In areas where the map the map is black, the grass will have no length and the shell will displace downward below the original geometry where it should not be seen.

An opacity mask can also be used to achieve the same effect though the displacement method is preferred as it renders without the extra time needed to calculate transparency. Because the displacement method generates no transparency it is a good candidate for using the fast rendering Primitive Hitmode feature of the AoA Advanced Lights.

Quick Start

Loading the grass shader onto an object in the scene.

The !Grass Shader Base preset can be found in the content tab under Shader Presets - Age of Armour - Grass.

Additional grass presets, created by Dimension Theory, are located in the subdirectory DT-Presets.

To apply grass to any object, select the object and any desired material zones then double click one of the presets.

If the grass looks very coarse or erratic you may find that using a finer Shading Rate (in the render settings) provides better results. Most of the product shots were rendered at a shading rates between 0.5 and 0.1 (smaller numbers providing better results).

Quick Tips

Patchy grass created using 3-WildGrassE preset and Min Displacement -1 on a geometry shell over a plane using the AoA Rock Shader.

General

Parameter Settings

Advanced Light Flags Group

The parameters of the Advanced Light Flags group contain settings for use with the AoA Advanced Lights.

The settings themselves do nothing to the appearance of the grass. They simply provide settings which can facilitate flagging when used along with the Advanced Ambient, Distant and Spot lights.

See the AoA Advanced Lights user guides for more information on flagging.

Diffuse Group

A comparative chart of renders illustrating the effects of the Color Variation setting of the AoA Grass Shader.

The parameters of the Diffuse group set the base colors and color variation of the grass.

Displacement Group

The settings of the Displacement group control, and allow for the masking of, the length of the grass.

In most cases, it is advisable that you use the Length setting in the Shape Group rather than any of the displacement settings.

However, the Minimum Displacement setting can be useful to lower the starting points of the grass to bring it below another surface when using a Displacement Mask for trails or when you desire the grass to grow in patches as illustrated earlier in this guide.

Opacity Group

The Opacity Group contains only one setting. Like the default DAZ Studio Shader this allows areas of the surface to be made invisible by use of a transparency map.

While this has its uses, it is recommended that you use the geometry shell and displacement mask method outlined earlier as transmapped surfaces tend to render more slowly.

Shape Group

A comparative chart showing the effects of the Clump Frequency and Strength settings of the AoA Grass Shader.

Here you will find parameters to adjust the length, shape randomization and the waving, or clumping, of the grass.

An important thing to keep in mind is that Clump Frequency, Clump Strength and Blade Thickness are somewhat tied together. Adjusting one setting may require a bit of fine tuning to another.

Though not a rule by any means, in general, the higher the Clump Frequency the lower the Clump Strength should be. If both these settings are high it may give th appearance of crab grass rather than "majestic waves of grain" though more leafy. When both these settings are high you may also want to lower the Blade Thickness to make the grass look less leafy.

Smoothing Group

The two settings in the smoothing group are unlikely to be needed for surfaces with grass but are included in the event a special need arises.

At this time neither of these settings have any effect on subdivided geometry.

Specular Group

Specular highlights can be useful to help accent the grass, giving it a wet, lush look. Because specular is very dependant on viewing angle it can also be used to help define shapes like accentuating changes in rolling hills.

With that said, you may want to use specular sparingly or at a low strength, particularly in large or distant scenes. Glossy highlights on distant grass can produce a speckled effect and less glossy highlights can sometimes appear waxy on large rolling hills.

Tiling Group

Tiling controls allow the repeating and shifting of images loaded into the Displacement Mask and Opacity Mask parameters. All other aspects of the Grass Shader are completely procedural so are unaffected by tiling.

Translucency Group

Two renders of a castle on a rolling hill illustrating the effect of translucency on the grass shader.

Translucency is a important part of the AoA Grass Shader. It provides extra realism by allowing some light to shine through the blades of grass, softening shadowed areas and giving rolling hills a velvety appearance.

Notice in the image above how the translucency not only brightens the grass but also gives visual ques which better show the rolls between the near and far hills.

UV Maps Group

Known Issues

Only on some SubD geometry - When tall grass is applied to a complex shape, such as Genesis with SubD applied, it is possible that some sections of grass may appear to be clipped.

The grass shader was intended to be used on more appropriate objects like lawns and terrains, however, should grass be used on complex objects such as a human figure, either turning off SubD for the object (Resolution Level - Base in the object's parameters tab) or using a large Bucket Size (in the DS render settings) may help eliminate the error.

Top Introduction Important Concepts Quick Start Parameter Settings