TrueType® fonts, created by Apple Computer and Adobe

Chapter 8, Problem 17E

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QUESTION:

TrueType® fonts, created by Apple Computer and Adobe Systems, use quadratic Bézier curves, while PostScript® fonts, created by Microsoft, use cubic Bézier curves. The cubic curves provide more flexibility for typeface design, but it is important to Microsoft that every typeface using quadratic curves can be transformed into one that uses cubic curves. Suppose that w(t) is a quadratic curve, with control points \(\mathbf{p}_{0}, \mathbf{p}_{1}, \text { and } \mathbf{p}_{2}\).

a. Find control points \(\mathbf{r}_{0}, \mathbf{r}_{1}, \mathbf{r}_{2}, \text { and } \mathbf{r}_{3}\) such that the cubic Bézier curve x(t) with these control points has the property that x(t) and w(t) have the same initial and terminal points and the same tangent vectors at t = 0 and t = 1. (See Exercise 16.)

b. Show that if x(t) is constructed as in part (a), then \(\mathbf{x}(t)=\mathbf{w}(t) \text { for } 0 \leq t \leq 1\).

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QUESTION:

TrueType® fonts, created by Apple Computer and Adobe Systems, use quadratic Bézier curves, while PostScript® fonts, created by Microsoft, use cubic Bézier curves. The cubic curves provide more flexibility for typeface design, but it is important to Microsoft that every typeface using quadratic curves can be transformed into one that uses cubic curves. Suppose that w(t) is a quadratic curve, with control points \(\mathbf{p}_{0}, \mathbf{p}_{1}, \text { and } \mathbf{p}_{2}\).

a. Find control points \(\mathbf{r}_{0}, \mathbf{r}_{1}, \mathbf{r}_{2}, \text { and } \mathbf{r}_{3}\) such that the cubic Bézier curve x(t) with these control points has the property that x(t) and w(t) have the same initial and terminal points and the same tangent vectors at t = 0 and t = 1. (See Exercise 16.)

b. Show that if x(t) is constructed as in part (a), then \(\mathbf{x}(t)=\mathbf{w}(t) \text { for } 0 \leq t \leq 1\).

ANSWER:

Solution 17E1. the control poi

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