Getting Started with Hothouse 3D

Hohouse includes an integrated help system which gives more detailed information on every aspect of creating and editing speces and generating and exporting plant models. Press F1 to show the context sensitive help window and then click on a part of the work bench for related help. Press F2 to search the user guide, or F3 to show the entire guide in a separate window (all shortcut keys can be displayed by pressing F12). Here is a quick overview.

The picture below shows the main areas of Hothouse's interface. The icons at the top left are used to show the species already in the database, which after installation will be the five sample speces. Species may be created, saved and deleted; you can export and randomise 3D models - you can edit the structure through the Explorer; adjust the level of detail for each part with the corresponding statistics shown as the detail changes.

A Hothouse Spece consists of one or more 'parts' (called Body Parts in the Explorer view above), and these parts are grown on other parts, using one or more growers (a hierarchy of which is to be found under Growth Plan above). In the example of the Red Maple there are a couple of leaf types (each with a separate appearance) and a couple of stem types - the trunk and the branch. The growth plan starts by growing a single trunk, and then grows branches on the trunk, and then leaves on the branches. Associated with each part is a material which describes the appearance of a part, and for leaves this is also the appearance at a particlar time of year. Multiple materials can be defined for a leaf for each different season; Hothouse then fades between them as the editor's season slider is moved.

Push the new spece icon in the main menu bar, type in the name of the new spece and give it an approximate size using the width and length sliders. Hothouse will create a few things to get you going: a leaf type and a couple of stem types (a trunk and a branch) are made; growers are created for growing branches on the trunk, and to grow leaves on the branches. The three parts and the three growers are displayed in the Explorer with the growers arranged below in a hiearchy. Selecting any of these items in the Explorer's tree will show the associated properties; for example, a stem part has length and curviness parameters, amongst others; a leaf grower needs to know how many leaves to grow and in which direction to grow them in.

Once you have a new default spece, a plant will be generated for it and shown in the Spece Viewer; the stems are created with a blank material and are shown in plain white. Each part's material needs to be given images to produce the required appearance; this will either mean using your own image files (*.bmp,*.jpg,*.png,...etc), or choosing a set of images provided in the samples folder. In the latter case select a material snapshot (there is initially one of these created for each part) , and press the Material button. This brings up the Material Editor where it is possible to provide separate images for diffuse, transmit, normal, specular and bump maps. To keep things simple for the moment just choose ' Import image folder...' which will open a file dialogue centred on Hothouse's samples directory. In this directory there are further bark and leaves directories which contain a few further directories which hold the images for each sample. Choose one of these last directories and press OK. By setting up the material in this way and providing your own images it is possible to generate the appearance you are looking for. This is what it looks like when MapleAutumn3 is imported for the leaves and OakBark2 is imported for the trunk's material. Note that a material for the branch does not have to be explicitly set up because, by default, it inherits its material from a stem further up the hierarchy.

The most important properties that affect the overall size and shape of each plant are made visible by selecting Spece Properties at the top of the Explorer's tree control. Two tabs then become visible: one for the overall spece scale (height) and width, and another tab for the pruning properties. The scale is considered to be the length of the trunk plus the length of any branches growing up from it. The width of the spece affects the width of the trunk and all subsequent stem levels, and the Width Decay affects how the width of a child stem is related to the width of the parent.

For our new spece, the shape was changed on the spece's pruning tab to 'Inverse conical', the branch part was made longer relative to the trunk part, the branch grower's 'down' and 'spread' angles were changed, and more leaves were grown by reducing the Separation distance on the leaf's grower.

Random plant to plant variations are specified using sliders like the one shown on the left; each slider has a center mark with a bar either side. Random numbers are then chosen by Hothouse between these two variance bars; 'Curve 1' on the example shown specifies values between -10° and +10°, 'Curve 2' between +10° and +50°.

New random numbers are chosen when a part or grower is first created and these numbers are kept across an editing session. To generate a completely new random plant, press the dice button.

Effect of Tesselation and Minimum Error

The effect of tesselation is shown below using a leaf. It can be seen that a small increase in the tesselation level can have a dramatic effect on the number of triangles produced, and in the usual case of many leaves on a tree or plant a tesselation level of 0 is probably the most appropriate. It can also be seen that when the mimum error is increased from zero, the number of triangles produced reduces; this is because only those triangles that fall on an area of the bump map with a height difference greater than the minimum error are split.

Tesselation	0	1	2	6	6 + min.error	6 + min.error
Triangles	2	8	32	5976	599	599

When tesselating stems, it is not just the bump map that is taken into account. The curvature both around the circumference and along the length of the stem also contributes to the error between ideal and approximate surfaces.

This trunk stem is shown with 18 triangles.

Keeping the same minimum error but bending the stem increases the detail around the curve; in this case to 168 triangles.

Decreasing the minimum error results in much greater detail which here resulted in 745 triangles.

Overrides

To review the effect of the minimum error at near and far levels of detail for the currently displayed models it is possible to select either the Near px or Far px columns of the part of interest. That part is then immediately tesselated at one of these extremes in both the main Spece Viewer and preview windows. To once again have the part tesselated with the correct interpolated minimum error at the current distance the Part column can be selected. To fix the minimum error for all parts the Lock level of detail button can be selected in the Spece Viewer; the model can then be zoomed in and out without changing the level of detail.