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<span id="Models"></span><div class="header">
<p>
Next: <a href="Lights.html" accesskey="n" rel="next">Lights</a>, Previous: <a href="Tile-Maps.html" accesskey="p" rel="prev">Tile Maps</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Models-1"></span><h4 class="subsection">5.3.8 Models</h4>
<p><em>Disclaimer: Chickadee is alpha software, but 3D model support is
even more alpha than that. There are many missing features in both
the model loading and rendering components, so set your expectations
accordingly!</em>
</p>
<p>The <code>(chickadee graphics model)</code> module provides procedures to
load and render 3D models in the classic OBJ and more modern glTF 2.0
formats.
</p>
<p>Here’s some basic boilerplate to render a 3D model:
</p>
<div class="example">
<pre class="example">(use-modules (chickadee graphics light)
(chickadee graphics model)
(chickadee graphics skybox))
(define model (load-gltf "Suzanne.gltf"))
(define camera-position (vec3 0.0 0.0 3.0))
(define world (make-identity-matrix4))
(define view (look-at camera-position (vec3 0.0 0.0 0.0) (vec3 0.0 1.0 0.0)))
(define projection (perspective-projection (/ pi 3.0) (/ 4.0 3.0) 0.1 5.0))
(define (draw alpha)
(with-projection projection
(draw-model model world view camera-position
</pre></div>
<dl>
<dt id="index-load_002dobj">Procedure: <strong>load-obj</strong> <em>file-name</em></dt>
<dd><p>Load the OBJ formatted model in <var>file-name</var> and return a 3D model
object.
</p>
<p>OBJ models are rendered using a Phong lighting model, which is a
work-in-progress.
</p></dd></dl>
<dl>
<dt id="index-load_002dgltf">Procedure: <strong>load-gltf</strong> <em>file-name</em></dt>
<dd><p>Load the glTF 2.0 formatted model in <var>file-name</var> and return a 3D
model object.
</p>
<p>glTF models are rendered using a physically based lighting model,
which is currently a stub to be implemented later.
</p></dd></dl>
<dl>
<dt id="index-model_003f">Procedure: <strong>model?</strong> <em>obj</em></dt>
<dd><p>Return <code>#t</code> if <var>obj</var> is a 3D model.
</p></dd></dl>
<dl>
<dt id="index-draw_002dmodel">Procedure: <strong>draw-model</strong> <em>model [#:model-matrix] [#:view-matrix] [#:camera-position (vec3 0 0 0)] [#:skybox] [#:lights '()]</em></dt>
<dd>
<p>Render <var>model</var> with the transformation matrices <var>model-matrix</var>
and <var>view-matrix</var> applied. <var>camera-position</var> is the world
position of the camera, for correct specular lighting calculations.
<var>skybox</var> is used to apply ambient lighting to the model.
<var>lights</var> contains all of the dynamic lights (see <a href="Lights.html">Lights</a>) that
should have an effect on the model.
</p></dd></dl>
<p>Models are composed of simpler data types: meshes, primitives, and
materials. Let’s start with materials. A material controls the
appearance of a 3D object. Is the object a rough stone? Or maybe a
smooth metal? Materials control all of this and more.
</p>
<p>There are two types of materials in Chickadee: Phong and PBR.
</p>
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Next: <a href="Lights.html" accesskey="n" rel="next">Lights</a>, Previous: <a href="Tile-Maps.html" accesskey="p" rel="prev">Tile Maps</a>, Up: <a href="Graphics.html" accesskey="u" rel="up">Graphics</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p>
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