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Techniques of Presentations & Rendering

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Mag B

on 21 October 2014

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Transcript of Techniques of Presentations & Rendering

Techniques of Presentations
and Rendering

Tonal Values!
Why tonal values are important?
Describe how light reveals the form of objects
Clarify the arrangements of forms in space
Depict the color and texture of surfaces
Scribbling
Hatching
Crosshatching
Stippling
Creating Tonal Values!
Require a gradual
building up or layering of strokes or dots
. The visual effect of each technique varies according to the
nature of the stroke, the medium, and the texture of the drawing surface
. Regardless of the shading technique we use, we must always
be fully aware of the tonal value being depicted
.
Spacing and density of the strokes or dots.
Contrast!
Visual texture, grain, and
direction of the strokes.
Be careful not to lose the white of the paper.
Covering the paper surface entirely can cause a drawing to lose depth and vitality
Hatching consists of a series of more or less
parallel lines
. The strokes may be
long or short, mechanically ruled or drawn freehand
, and executed with either a
pen or a pencil on smooth or rough paper
. When spaced
close
enough together, the lines
lose their individuality and merge to form a tonal value
. We therefore
rely primarily on the spacing and density of lines to control the lightness or darkness of a value
. While
thickening
the linear strokes can
serve to deepen the darkest values
, using
too thick of a line can result in an unintentional coarseness and heaviness of texture
.

The
direction of hatching
can also follow the contours of a form and
emphasize the orientation of its surfaces
. Remember that direction alone, however, has no impact on tonal value.
With texture and contour
, the series of lines c
an also convey material characteristics
, such as the
grain of wood
, the
marbling of stone
, or the
weave of fabric
.
Crosshatching utilizes
two or more series of parallel lines to create tonal values
. As with hatching, the s
trokes may be be long or short
,
mechanically ruled or drawn freehand
, and executed with either a
pen or a pencil on smooth or rough paper
.


Hatching and crosshatching
are often
combined into a single technique
. While simple
hatching creates the lighter
range of values in a drawing, c
rosshatching renders the darker range
.
Scribbling is a shading technique that involves drawing a network of
random, multidirectional lines
. The
freehand
nature of scribbling gives us great
flexibility in describing tonal values and textures
. We can v
ary the shape, density, and direction of the strokes
to achieve a wide range of tonal values, textures, and visual expression.
Stippling is a technique for shading by means of
very fine dots
. Applying stippling is a
slow and time-consuming
procedure that requires the
utmost patience and care in controlling the size and spacing of the dots
. The best results occur when using a
fine-tipped ink pen on a smooth drawing surface
.
Value Scale
Hatching
Stippling
Scribbling
Crosshatching
Vision results from the stimulation of
nerve cells in the retina of the eye
, signaling patterns of light intensity and color. Our visual system processes these
patterns of light and dark
. and is able to extract specific features of our e
nvironment-edges, contours, size, movement, and colo
r. If seeing patterns of light and dark is essential to our perception of objects, then establishing contrasts in
value discernible
to the eye is the
key to the graphic definition of light, form, and space.
We should always be aware of this
relationship
between
tonal value and texture
, whether
smooth or rough, hard or soft, polished or dull
. In most cases, tonal value is more critical than texture to the representation of light, shade, and the way they model forms in space.
Appearance of stone, the grain of wood, and the weave of a fabric. This is tactile texture that can be felt by touch.
Texture; smoothness or toughness?
Contrast!
heavy line weight to outline the cut elements
projects the cut elements forward with a dark value
reverses the value system and renders the cut elements as light figures against a dark field
Notice: the relationship of the building to the supporting ground mass is clearly indicated by the manner in which the ground is given a value similar to that of the cut elements of the building.
Shade & Shadows
Modeling Form
Shade refers to the relatively dark area on those parts of a solid that are tangent to or turned away from a theoretical light source
Shadows are t he relatively dark figures cast upon a surface by an opaque body or part of a body intercepting the rays from a theoretical light source
A shade line or casting edge separates an illuminated surface from one in shade.

A shadow line is the shadow cast by a shade line on a receiving surface.

A shadow plane is a plane of light rays that passes through adjacent points of a straight line.
Hard edges delineate sharp, angular breaks in form or describe contours that are separated from the background by some intervening space. We define hard edges with an abrupt and incisive shift in tonal value.
Soft edges describe indistinct or vague background shapes, gently curving surfaces and rounded forms, and areas of low contrast. We create soft edges with a gradual change in tonal value or diffuse tonal contrast.
Light values occur on any surface turned toward the light source.
Tonal values shift as a surface turns away from the light source, with intermediate values occurring on surfaces that are tangent to the direction of the light rays.
Highlights appear as luminous spots on smooth surfaces that directly face or mirror the light source.
Shade refers to the comparatively dark values of surfaces that are turned away from the light source.
Shadows are dark values cast by an object or part of an object upon a surface that would otherwise be illuminated by the light source.
Areas of reflected light-light cast back from a nearby surface-lighten the tonal value of a portion of a shaded surface or a shadow.
Tonal value is the graphic equivalent of shade and shadow, and can only indicate light by describing its absence.
Maged Elsamny, PhD
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