Metaball drawing system, metaball drawing method, and memory medium storing metaball drawing program

A metaball drawing system comprising:

• a metaball definition system that defines first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions, a first set of first red data, first green data and first blue data being assigned to said first metaball, a second set of second red data, second green data and second blue data being assigned to said second metaball;
• a threshold setting system that sets a threshold band with respect to said first and second density distributions;
• a first metaball determination system that determines whether a pixel on said screen is included in said first metaball;
• a first density calculation system that calculates a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball by said first metaball determination system;
• a first threshold determination system that determines whether said first density falls within said threshold band;
• a first color density calculation system that calculates a first red density, a first green density and a first blue density from said first set of first red data, first green data and first blue data based on said first density when it is determined that said first density falls within said threshold band by said first threshold determination system;
• a first luminance-value setting system that sets a first luminance value in said pixel based on said first red density, said first green density and said first blue density;
• a second metaball determination system that determines whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball;
• a second density calculation system that calculates a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball by said second metaball determination system;
• a second threshold determination system that determines whether said second density falls within said threshold band;
• a second color density calculation system that calculates a second red density, a second green density and a second blue density from said first set of first red data, first green data and first blue data and said second set of second red data, second green data and second blue data based on said second density when it is determined that said second density falls within said threshold band by said second threshold determination system;
• and
• a second luminance-value setting system that sets a second luminance value in said pixel based on said second red density, said second green density and said second blue density.

A metaball drawing method performed by a metaball drawing system, comprising:

• defining first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions;
• setting a threshold band with respect to said first and second density distributions;
• determining whether a pixel on said screen is included in said first metaball;
• calculating a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball;
• determining whether said first density falls within said threshold band;
• setting a first luminance value in said pixel based on said first density when it is determined that said first density falls within said threshold band;
• determining whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball;
• calculating a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball;
• determining whether said second density falls within said threshold band;
• and
• setting a second luminance value in said pixel based on said second density when it is determined that said second density falls within said threshold band.

A metaball drawing method performed by a metaball drawing system, comprising:

• defining first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions, a first set of first red data, first green data and first blue data being assigned to said first metaball, a second set of second red data, second green data and second blue data being assigned to said second metaball;
• setting a threshold band with respect to said first and second density distributions;
• determining whether a pixel is included in said first metaball;
• calculating a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball;
• determining whether said first density falls within said threshold band;
• calculating a first red density, a first green density and a first blue density from said first set of first red data, first green data and first blue data based on said first density when it is determined that said first density falls within said threshold band;
• setting a first luminance value in said pixel based on said first red density, first green density and first blue density;
• determining whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball;
• calculating a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball;
• determining whether said second density falls within said threshold band;
• calculating a second red density, a second green density and a second blue density from said first set of first red data, first green data and first blue data and said second set of second red data, second green data and second blue data based on said second density when it is determined that said second density falls within said threshold band;
• and
• setting a second luminance value in said pixel based on said second red density, second green density and second blue density.

A memory medium storing a metaball drawing program, which when executed by a system control unit, performs procedures comprising:

• a procedure of defining first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions;
• a procedure of setting a threshold band with respect to said first and second density distributions;
• a procedure of determining whether a pixel on said screen is included in said first metaball;
• a procedure of calculating a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball;
• a procedure of determining whether said first density falls within said threshold band;
• a procedure of setting a first luminance value in said pixel based on said first density when it is determined that said first density falls within said threshold band;
• a procedure of determining whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball;
• a procedure of calculating a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball;
• a procedure of determining whether said second density falls within said threshold band;
• and
• a procedure of setting a second luminance value in said pixel based on said second density when it is determined that said second density falls within said threshold band.

A memory medium storing a metaball drawing program, which when executed by a system control unit, performs procedures comprising:

• a procedure of defining first and second metaballs with respect to a screen, said respective first and second metaballs being represented by first and second density distributions, a first set of first red data, first green data and first blue data being assigned to said first metaball, a second set of second red data, second green data and second blue data being assigned to said second metaball;
• a procedure of setting a threshold band with respect to said first and second density distributions;
• a procedure of determining whether a pixel is included in said first metaball;
• a procedure of calculating a first density at said pixel based on said first density distribution when it is determined that said pixel is included in said first metaball;
• a procedure of determining whether said first density falls within said threshold band;
• a procedure of calculating a first red density, a first green density and a first blue density from said first set of first red data, first green data and first blue data based on said first density when it is determined that said first density falls within said threshold band;
• a procedure of setting a first luminance value in said pixel based on said first red density, green density and blue density;
• a procedure of determining whether said pixel is included in said second metaball after it is determined whether said pixel is included in said first metaball;
• a procedure of calculating a second density at said pixel based on a density distribution, which is combined by said first and second density distributions, when it is determined that said pixel is included in said second metaball;
• a procedure of determining whether said second density falls within said threshold band;
• a procedure of calculating a second red density, a green density and a blue density at said pixel from said first set of first red data, first green data and first blue data and said second set of second red data, second green data and second blue data based on said second density when it is determined that said second density falls within said threshold band;
• and
• a procedure of setting a second luminance value in said pixel based on said second red density, second green density and second blue density.