mjbWorld program - ElivationGrid

ElevationGrid {

eventIn MFFloat set_height
exposedField SFNode color NULL
exposedField SFNode normal NULL
exposedField SFNode texCoord NULL
field MFFloat height [] # (-,)
field SFBool ccw TRUE
field SFBool colorPerVertex TRUE
field SFFloat creaseAngle 0 # [0,]
field SFBool normalPerVertex TRUE
field SFBool solid TRUE
field SFInt32 xDimension 0 # [0,)
field SFFloat xSpacing 1.0 # (0,)
field SFInt32 zDimension 0 # [0,)
field SFFloat zSpacing 1.0 # (0,)

}

The ElevationGrid node specifies a uniform rectangular grid of varying height in the Y=0 plane of the local coordinate system. The geometry is
described by a scalar array of height values that specify the height of a surface above each point of the grid.

The xDimension and zDimension fields indicate the number of elements of the grid height array in the X and Z directions. Both xDimension and
zDimension shall be greater than or equal to zero. If either the xDimension or the zDimension is less than two, the ElevationGrid contains no
quadrilaterals. The vertex locations for the rectangles are defined by the height field and the xSpacing and zSpacing fields:

The height field is an xDimension by zDimension array of scalar values representing the height above the grid for each vertex.
The xSpacing and zSpacing fields indicate the distance between vertices in the X and Z directions respectively, and shall be greater than
zero.

Thus, the vertex corresponding to the point P[i, j] on the grid is placed at:

P[i,j].x = xSpacing × i
P[i,j].y = height[ i + j × xDimension]
P[i,j].z = zSpacing × j

where 0 <= i < xDimension and 0 <= j < zDimension,
and P[0,0] is height[0] units above/below the origin of the local
coordinate system

The set_height eventIn allows the height MFFloat field to be changed to support animated ElevationGrid nodes.

The color field specifies per-vertex or per-quadrilateral colours for the ElevationGrid node depending on the value of colorPerVertex. If the color
field is NULL, the ElevationGrid node is rendered with the overall attributes of the Shape node enclosing the ElevationGrid node (see
4.14, Lighting model).

The colorPerVertex field determines whether colours specified in the color field are applied to each vertex or each quadrilateral of the
ElevationGrid node. If colorPerVertex is FALSE and the color field is not NULL, the color field shall specify a Color node containing at least
(xDimension-1)×(zDimension-1) colours; one for each quadrilateral, ordered as follows:

QuadColor[i,j] = Color[ i + j × (xDimension-1)]

where 0 <= i < xDimension-1 and 0 <= j < zDimension-1,
and QuadColor[i,j] is the colour for the quadrilateral defined
by height[i+j×xDimension], height[(i+1)+j×xDimension],
height[(i+1)+(j+1)×xDimension] and height[i+(j+1)×xDimension]

If colorPerVertex is TRUE and the color field is not NULL, the color field shall specify a Color node containing at least
xDimension × zDimension colours, one for each vertex, ordered as follows:

VertexColor[i,j] = Color[ i + j × xDimension]

where 0 <= i < xDimension and 0 <= j < zDimension,
and VertexColor[i,j] is the colour for the vertex defined by
height[i+j×xDimension]

The normal field specifies per-vertex or per-quadrilateral normals for the ElevationGrid node. If the normal field is NULL, the browser shall
automatically generate normals, using the creaseAngle field to determine if and how normals are smoothed across the surface (see 4.6.3.5, Crease
angle field).

The normalPerVertex field determines whether normals are applied to each vertex or each quadrilateral of the ElevationGrid node depending on
the value of normalPerVertex. If normalPerVertex is FALSE and the normal node is not NULL, the normal field shall specify a Normal node
containing at least (xDimension-1)×(zDimension-1) normals; one for each quadrilateral, ordered as follows:

QuadNormal[i,j] = Normal[ i + j × (xDimension-1)]

where 0 <= i < xDimension-1 and 0 <= j < zDimension-1,
and QuadNormal[i,j] is the normal for the quadrilateral defined
by height[i+j×xDimension], height[(i+1)+j×xDimension],
height[(i+1)+(j+1)×xDimension] and height[i+(j+1)×xDimension]

If normalPerVertex is TRUE and the normal field is not NULL, the normal field shall specify a Normal node containing at least
xDimension × zDimension normals; one for each vertex, ordered as follows:

VertexNormal[i,j] = Normal[ i + j × xDimension]

where 0 <= i < xDimension and 0 <= j < zDimension,
and VertexNormal[i,j] is the normal for the vertex defined
by height[i+j×xDimension]

The texCoord field specifies per-vertex texture coordinates for the ElevationGrid node. If texCoord is NULL, default texture coordinates are
applied to the geometry. The default texture coordinates range from (0,0) at the first vertex to (1,1) at the last vertex. The S texture coordinate is
aligned with the positive X-axis, and the T texture coordinate with positive Z-axis. If texCoord is not NULL, it shall specify a TextureCoordinate
node containing at least (xDimension)×(zDimension) texture coordinates; one for each vertex, ordered as follows:

VertexTexCoord[i,j] = TextureCoordinate[ i + j × xDimension]

where 0 <= i < xDimension and 0 <= j < zDimension,
and VertexTexCoord[i,j] is the texture coordinate for the vertex
defined by height[i+j×xDimension]

The ccw, solid, and creaseAngle fields are described in 4.6.3, Shapes and geometry.

By default, the quadrilaterals are defined with a counterclockwise ordering. Hence, the Y-component of the normal is positive. Setting the ccw field
to FALSE reverses the normal direction. Backface culling is enabled when the solid field is TRUE.

See Figure 6.5 for a depiction of the ElevationGrid node.


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