Question

我在iPhone上有一个基于2D平铺的OpenGL ES游戏，当与游戏中的角色交谈时，屏幕上会出现一个对话框。我想知道如何逐渐显示文本（位图字体），而不是一次显示整个字符串，但是，他们如何在塞尔达游戏中这样做，逐字母与小命令提示符看下划线引导文本...有谁知道我在说什么？

P.S。 - 我目前使用一个名为-drawStringAtPoint（AngelCode位图 - 字体库）的方法通过位图字体在屏幕上获取我的字符串。但我无法弄清楚如何做多行或一点一点地显示文字......

//From AngelCodeFont.m

// Changed 07/05/09 to add kerning
- (void)drawStringAt:(CGPoint)point text:(NSString*)text {

    // TODO: Add error if string is too long using NSASSERT
    //NSAssert(1>0, @"WARNING: Text to be rendered is too long");

    // Reset the number of quads which are going to be drawn
    int currentQuad = 0;

    // Enable those states necessary to draw with textures and allow blending
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_BLEND);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);

    // Setup how the text is to be blended
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    // Bind to the texture which was generated for the spritesheet image used for this font.  We only
    // need to bind once before the drawing as all characters are on the same texture.
    if([[image texture] name] != [_director currentlyBoundTexture]) {
        [_director setCurrentlyBoundTexture:[[image texture] name]];
        glBindTexture(GL_TEXTURE_2D, [[image texture] name]);
    }   

    // Set up the previous character and kerning amount vars
    unichar previousChar = -1;
    int kerningAmount = 0;

    // Loop through all the characters in the text
    for(int i=0; i<[text length]; i++) {

        // Grab the unicode value of the current character
        unichar charID = [text characterAtIndex:i];

        // Look up the kerning information for the previous char and this current char
        kerningAmount = [self kerningAmountForFirst:previousChar second:charID];

        // Move x based on the kerning info
        point.x += kerningAmount * scale;

        // Only render the current character if it is going to be visible otherwise move the variables such as currentQuad and point.x
        // as normal but don't render the character which should save some cycles
        if(point.x > 0 - ([charsArray[charID] width] * scale) || point.x < [[UIScreen mainScreen] bounds].size.width || point.y > 0 - ([charsArray[charID] height] * scale) || point.y < [[UIScreen mainScreen] bounds].size.height) {

            // Using the current x and y, calculate the correct position of the character using the x and y offsets for each character.
            // This will cause the characters to all sit on the line correctly with tails below the line etc.
            CGPoint newPoint = CGPointMake(point.x, 
                                           point.y - ([charsArray[charID] yOffset] + [charsArray[charID] height]) * [charsArray[charID] scale]);

            // Create a point into the bitmap font spritesheet using the coords read from the control file for this character
            CGPoint pointOffset = CGPointMake([charsArray[charID] x], [charsArray[charID] y]);

            // Calculate the texture coordinates and quad vertices for the current character
            [[charsArray[charID] image] calculateTexCoordsAtOffset:pointOffset subImageWidth:[charsArray[charID] width] subImageHeight:[charsArray[charID] height]];
            [[charsArray[charID] image] calculateVerticesAtPoint:newPoint subImageWidth:[charsArray[charID] width] subImageHeight:[charsArray[charID] height] centerOfImage:NO];

            // Place the calculated texture coordinates and quad vertices into the arrays we will use when drawing our string
            texCoords[currentQuad] = *[[charsArray[charID] image] textureCoordinates];
            vertices[currentQuad] = *[[charsArray[charID] image] vertices];

            // Increment the Quad count
            currentQuad++;
        }

        // Move x based on the amount to advance for the current char
        point.x += [charsArray[charID] xAdvance] * scale;

        // Store the character just processed as the previous char for looking up any kerning info
        previousChar = charID;
    }

    // Now that we have calculated all the quads and textures for the string we are drawing we can draw them all
    glVertexPointer(2, GL_FLOAT, 0, vertices);
    glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
    glColor4f(colourFilter.red, colourFilter.green, colourFilter.blue, colourFilter.alpha * [_director globalAlpha]);
    glDrawElements(GL_TRIANGLES, currentQuad*6, GL_UNSIGNED_SHORT, indices);
    glDisable(GL_TEXTURE_2D);
    glDisable(GL_BLEND);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_VERTEX_ARRAY);
}

Answer 1

只需多次绘制文本，每次在字符串中再包含一个字符。

在伪代码中：

n = string length
for i=0 to n-1 {
    draw_text(substring from 0 to i + the underscore character)
    wait a couple of milliseconds
}
draw_text(entire string without the underscore character)

显然，等待“几毫秒”自然会使一切停止，所以这必须在一个单独的线程中发生，或者作为游戏循环中的勾号发生。

Answer 2

为i = 0做 - >＆gt; n -1 {draw text}表示渲染文本时不会发生任何其他情况。像对待其他任何内容一样为输入文本效果设置动画，使用绘制之间的tickcount为帧速率独立动画速度增加动画状态。

struct FancyText
{
  char *text;
  double cps; // chars per second
  double len = 0;
}

void render(CGpoint* point, FancyText *fancy, double delta)
{
  fancy->index += delta * cps;

  drawStringAt(point, fancy->text, floor(index));
}

void drawStringAt(CGpoint *point, char *text)
{
  drawStringAt(point, text, strlen(text));
}

void drawStringAt(CGPoint *point, char *text, int len)
{
  // your drawstring code
  // using for i = 0 -> len - 1 instead of strlen(text)
}

如何获得塞尔达文字效果？

2 个答案: